Systems for recovery communications via airborne platforms

ABSTRACT

A communications system for providing recovery communication service to users in a coverage area affected by an emergency disruption of normal communication services. The system comprises a ground hub serving as a gateway to terrestrial networks including a dispatch center and configured to communicate with at least three mobile airborne platforms roving over the coverage area via respective feeder-links in a Ku or Ka band. A first mobile airborne platform communicates in a first frequency band with emergency workers that are working in the coverage area and associated with the dispatch center. A second mobile airborne platform communicates, in place of at least one disrupted base station in the coverage area, with user mobile phones in mobile phone frequency bands or user personal devices in WiFi bands located in the coverage area. A third mobile airborne platform generates real-time imaging of surfaces located in the coverage area.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13778175, filed on Feb. 27, 2013, entitled “Communications ArchitecturesVia UAV”. This application is related to U.S. patent application Ser.No. 13/623,882, filed on Sep. 21, 2012, entitled “Concurrent AirborneCommunication Methods and Systems”, now U.S. Pat. No. 8,767,615, issuedon Jul. 1, 2014; and U.S. patent application Ser. No. 13/778,171, filedon Feb. 27, 2013, entitled “Multi-Channel Communication OptimizationMethods and Systems”, now U.S. Pat. No. 9,596,024, issued on Mar. 14,2017, both of which are incorporated herein by reference in theirentireties.

TECHNICAL FIELD

This disclosure describes exemplary embodiments on improving theoperation and use of airborne communication methods and systems such asthrough concurrent data delivery with redundancy and privacy ranking andrelated calibration. The present invention relates to smart antennamethods on UAVs providing emergency and disaster communications servicesfor the rescue teams and the community in a disaster area. There are twosets of payloads; one in foreground to interface with users and theother in the background, connecting to a gateway which may communicatewith other communications infrastructures.

BACKGROUND

When disasters happen, many terrestrial infrastructures including cellphones and Internet services become less functional. For emergency anddisaster recovery systems, there are needs for real time communicationsto residents, and rescue workers in disaster areas. It is also importantfor access of surveillances (videos and images) data over the areas.Unmanned Aerial Vehicle (UAVs) will be very useful tools for thesepeaceful missions. The proposed systems with three real time functionsrequire for peaceful missions;

-   -   1. An ad hoc communications network for local residents,        operating in commercial cell phone bands, and/or Wifi bands    -   2. An ad hoc communications network for rescue works, operating        in emergency bands, and

3. Communications from air mobile surveillance platforms for videos andimages to a central hub.

It is possible to perform all three functions in a large UAV. However,each of the functions may be performed and/or supported by a small UAV.In some embodiments, limits on communications payloads on an UAV may beallocated; such as ˜20 Kg in weight, and 200 W power consumptions, andmission flight time of 12 hours at altitudes at least above the“terrestrial weather” initially. It may also be preferred that the UAVsfly above 5 Km in altitudes.

There are four technologies in architectures for emergency services:

-   -   a. UAV as communications nodes    -   b. Foreground communications networks between users and UAVs        -   For users with hand-held devices        -   utilizing remote-beam forming network(RBFN) with the ground            based beam forming (GBBF) facility    -   c. Background communications networks, (back channels or        feeder-links) between ground infrastructures/facilities and UAVs        -   Back-channels or feeder-links between UAVs and GBBF            processing centers.    -   d. Wavefront multiplexing/de-multiplexing (WF muxing/demuxing);        -   Back-channel calibrations on feeder-link transmission for            RBFN/GBBF        -   Coherent power combining in receivers on signals from            different channels on various UAV ;        -   Secured transmissions with redundancies via UAVs

Multiple smaller UAVs may be “combined” to perform a function, saycommunicating with local residents when their cell towers becomenon-functional. We may fast-deploy 4 small UAVs and group them viacommunications networks to replace the functions of ill functioned localcell towers or base-stations which are damaged due to currentemergencies or disasters. The residents may use their existing personalcommunications devices including their cell phones to communicate tooutside worlds via the ad hoc communications network via these smallUAVs. In these cases, we may allocate SW&P limits on communicationspayloads on a small UAV; about <5 Kg in weight, and <50 W powerconsumptions.

The payloads on surveillance platforms will use optical sensors togenerate optical images during day time. There are possibilities ofusing optical illuminators on the UAVs or different UAVs to allow nightoperations. Infrared sensors may also be used for night visions andimaging.

Microwave sensors can be used for both night and cloudy (or raining)conditions in which optical sensors may not function well. Activemonostatic Radars may be deployed by individual UAVs. Polystatic ormulti-static Radars can be deployed via a fleet of UAVs.

Multiple UAVs will be coordinated to form a coherent RF receiving systemas a passive Radar receiver via GBBF processing and real time knowledgeof the positions/orientations of all receiving elements on various UAVplatforms. It will take advantage of ground reflections of existing andknown RF illuminators such as Navstar satellite from GPS constellations,or satellites from many other GNSS constellations at L-band. It is alsopossible to use as RF illuminators by taking advantages of groundreflections of high power radiations by many direct broadcastingsatellites (DBS), which illuminate “land mass” with high EIRP over 500MHz instantaneous bandwidths (of known signals) at S, Ku and/or Ka band.The “known signals” are received signals through a direct path or asecond path from the same radiating DBS satellite. Furthermore, highpower radiations from Ka spot beams of recently deployed satellites onmany satellites either in geostationary or non-geostationary orbits, canalso be used as RF illuminators.

The terms of UHF, L, S, C, X, Ku, and Ka bands are following thedefinitions of IEEE US standard repeated in Table-1

TABLE 1 IEEE Designated Frequency Bands Table of IEEE band BandFrequency range Origin of name¹ HF band 3 to 30 MHz High Frequency VHFband 30 to 300 MHz Very High Frequency UHF band 300 to 1000 MHz UltraHigh Frequency L band 1 to 2 GHz Long wave S band 2 to 4 GHz Short waveC band 4 to 8 GHz Compromise between S and X X band 8 to 12 GHz Used inWW II for fire control, X for cross (as in crosshair) K_(u) band 12 to18 GHz Kurz-under K band 18 to 27 GHz German Kurz (short) K_(a) band 27to 40 GHz Kurz-above V band 40 to 75 GHz W band 75 to 110 GHz W followsV in the alphabet mm band 110 to 300 GHz

FIG. 1 illustrates a scenario of UAV's in a rescue mission. Three vitaltasks are provided by the UAVs;

-   -   1. Communications networks deployment for local residents in        disaster areas using their existing cell phones        -   UAV (M1) becomes the replacement of the damaged cell towers            in a Spoke-and-hub architecture        -   Residents can use their own cell phones ask for assistance            when needed    -   2. Communications networks deployment for rescue teams with        special phones        -   UAV (M2) becomes the rapid deployed cell towers for            communications among the rescue team members and their            dispatchers        -   Using separated emergency frequency bands        -   Spoke-and-hub architecture    -   3. Surveillance platforms for visual observations        -   UAV (M3) takes videos on disaster areas and relays them back            to the hub instantaneously        -   Dedicated high data rate links

All three major tasks will have the same hub which shall have capabilityto relay the emergency information to the mission authority. Users onthe two networks can communicate among themselves through the gatewayswhich are co-located at the same hub, which shall be standard mobilehubs that telecommunications service providers can support

An example of desired designs of the communications functions in thisdisclosure is summarized as follows:

-   -   In the airborne segment        -   Using 16 elements as array for foreground communications            network        -   to enable a 4-element subarray with multiple beam capability            maintaining links for data rate at 10 Mbps for each            subarray.        -   To enable a sparse array made from 4 subarrays at S/L bands            or C-band with multiple beam capability maintaining links            for data rate at 10 Mbps per beam.        -   To design Ku- band feeder links with a bandwidth at 160 MHz    -   In the user segment        -   Regular cell phones for the residents in the serviced            community        -   Common rescue mission equipment at 4.9 GHz    -   In the ground segment        -   Three Ku band antennas to track three UAVs concurrently            individually with data rate at 150 MHz back channel            bandwidths in both directions.        -   GBBF capability with knowledge of evolving array            orientations on UAVs

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 depicts a scenario of using three separated UAVs as three mobileplatforms for emergency and disaster recovery services; UAV M1 forcommunications among rescue team members, UAV M2 for communications asemergency replacements of mobile and/or fixed wireless base stations forresident communications via their existing mobile phones and/or personalcommunications devices using WiFi. UAV M3 for surveillances via optical,infrared, and RF sensors.

FIG. 2 depicts a simplified block diagram for a mobile communicationsvia UAV with on-board beam forming network (BFN) to mobile users using“foreground” links at L/S band. The ground interconnection toterrestrial communications facility are through feeder-links in Ku or Kaband. Feeder-links are also referred to as back-ground links, or backchannels.

FIG. 3 depicts a simplified block diagram for a mobile communicationsvia UAV to mobile users using “foreground” links at L/S band. The groundbased beam forming (GBBF) network and ground interconnection toterrestrial communications facility are through feeder-links in Ku or Kaband. Feeder-links are also referred to as back-ground links, or backchannels.

FIG. 4 depicts an operational scenario for a UAV with ground based beamforming through feeder-links, and foreground links for users. The UAVbased communications features multiple beams foreground communications.

FIG. 5 depicts an operational scenario for multiple UAVs in a closelyspace formation with ground based beam forming through feeder-links, andforeground links for users. The UAVs are spaced by orders of meters orless. The multiple-UAV based communications features multiple beamsforeground communications.

FIG. 6 depicts an operational scenario for multiple UAVs in a formationwith ground based beam forming through feeder-links, and foregroundlinks for users. The UAVs are spaced by orders of Kilo-meters. Themultiple-UAV based communications features multiple beams foregroundcommunications. Users with terminals of multiple tracking beams can takeadvantages of the multiple UAVs to achieve multiple folds of channelcapacity via frequency reuse.

FIG. 7 depicts an operational scenario for multiple UAVs in a formationwith ground based beam forming through feeder-links, and foregroundlinks for users. The UAVs are spaced by orders of Kilo-meters. Themultiple-UAV based communications features multiple beams foregroundcommunications. Wavefront multiplexing/demultiplexing (WFmuxing/demuxing) techniques are used to allow “coherent” power combiningof the radiated power from various UAVs in foreground links at userterminals or ground hubs. Users with terminals of multiple trackingbeams can take more advantages of the multiple UAVs to achieve multiplefolds of channel capacity via frequency reuse.

FIGS. 7a and 7b illustrate the operational principle of “coherent powercombining” and signal multiplexing via multi-channel waveforms inreceivers for three separated users through WF muxing/demuxingtechniques. FIG. 7a is a functional block diagram for forward link, andFIG. 7b is a functional block diagram for return link.

FIGS. 8a, 8b, and 8c illustrate the operational principle of wavefrontmultiplexing/demultiplexing for redundancy and signal security for oneuser. FIG. 8a is a functional block diagram for forward link, and FIG.8b a functional block diagram for return link. FIG. 8c depicts anumerical example of non-coherent data delivery by WF muxing/demuxingtechniques via 4 UAVs concurrently. It works for both forward and returnlinks.

FIGS. 9a, 9b, and 9c illustrate the feeder-link calibration andcompensations via principle of wavefront multiplexing/demultiplexing.FIG. 9a is a functional block diagram for forward link with on-boardoptimization processing; FIG. 9b is a functional block diagram forforward link with a pre-distortion technique with an on-groundoptimization processing; and FIG. 9c is a functional block diagram forreturn link with an on-ground optimization processing.

FIGS. 10a, 10b, and 10c illustrate the operational principle of“coherent power combining” and signal multiplexing via multi-channelwaveforms in receivers for three separated users through WFmuxing/demuxing techniques. All are simplified block diagrams showing aWF muxing operation in signal sources and a WF demuxing operation in adestination for forward links. FIG. 10a is a functional block diagramfor a forward link from a ground hub to a first user; FIG. 10b is afunctional block diagram for a forward link from a ground hub to asecond user; and FIG. 10c is a functional block diagram for a forwardlink from a ground hub to a third user.

FIG. 11 depicts a functional block diagrams for an on-boardretro-directive antennas for Ku/Ka feeder-link inter-connecting a groundprocessing facility and a UAV which anchoring the retro-directiveantenna.

FIG. 12 depicts inter-connectivity among three functional blocks ofmobile communication architecture via a UAV with 4-element array infeeder-links and GBBF; (1) on board return link payload and feeder-linkpayload, (2) ground processing facility with ground based beam forming,and (3) on board feeder-link payload and forward link payload. The firstlevel functional details of all three functional blocks are illustrated.On-board feeder links are implemented by a 4-element active array withbeam forming network. There are no beam forming for the foregroundcommunications payloads

FIG. 12a depicts inter-connectivity among three functional blocks ofmobile communication architecture via a UAV with 4-element array infeeder-links and GBBF; (1) on board return link payload and feeder-linkpayload, (2) ground processing facility with ground based beam forming,and (3) on board feeder-link payload and forward link payload. The firstlevel functional details of all three functional blocks are illustrated.On-board feeder links are implemented by a 4-element retro-directiveantenna.

FIG. 12b depicts inter-connectivity among three functional blocks ofmobile communication architecture via a UAV with 4-element array infeeder-links and GBBF; (1) on board return link payload with on-boardbeam forming network and feeder-link payload, (2) ground processingfacility but without ground based beam forming, and (3) on boardfeeder-link payload and forward link payload with onboard beam-formingnetwork. The first level functional details of all three functionalblocks are illustrated. On-board feeder links are implemented by a4-element retro-directive antenna.

FIG. 13a depicts two on board functional blocks of mobile communicationarchitecture with GBBF via a UAV with 4-element array in feeder-linkssimilar to FIG. 12a . The additions to FIG. 12a are feeder-linkcalibration and compensation mechanisms via Wavefront muxing/demuxingfor both forward and return links. (a) on board return link payload andfeeder-link payload with on-board optimization for forward link, and (b)on board feeder-link payload and forward link payload. On-board feederlinks are implemented by a 4-element retro-directive antenna.

FIG. 13b depicts a functional blocks of mobile communicationarchitecture with GBBF for ground processing facility with calibrationand compensation mechanisms via Wavefront muxing/demuxing for bothforward and return links. An optimization loop for return link WFdemuxing is on-ground.

FIG. 14a depicts two on board functional blocks of mobile communicationarchitecture with GBBF via a UAV with 4-element array in feeder-linkssimilar to FIG. 12a . The additions to FIG. 12a are feeder-linkcalibration and compensation mechanisms via Wavefront muxing/demuxingfor both forward and return links; (a) on board return link payload andfeeder-link payload without on-board optimization for forward link, and(b) on board feeder-link payload and forward link payload. On-boardfeeder links are implemented by a 4-element retro-directive antenna.

FIG. 14b depicts a functional blocks of mobile communicationarchitecture with GBBF for ground processing facility with calibrationand compensation mechanisms via Wavefront muxing/demuxing for bothforward and return links. An optimization loop for forward link WFdemuxing is implemented on-ground as pre-distortion techniques fordifferential phase and amplitude equalizations. A separated optimizationloop for return link WF demuxing is also implemented on-ground.

FIG. 15 depicts functional block diagrams of two digital beam forming(DBF) processors in a GBBF for ground processing facility; one for amultiple-beam transmitting (Tx) DBF and the other one for amultiple-beam receiving (Rx) DBF.

FIG. 16 features a slight deviation of FIG. 1; depicting a scenario ofusing three separated UAVs as three mobile platforms for emergency anddisaster recovery services; UAV M1 for communications among rescue teammembers, UAV M2 for communications as emergency replacements of mobileand/or fixed wireless base stations for resident communications viatheir existing mobile phones and/or personal communications devicesusing WiFi. UAV M4 for surveillances via RF sensors using satellites asRF illuminators.

DETAILED DESCRIPTION

FIG. 1 depicts a scenario of using three separated UAVs 120 as threemobile platforms for emergency and disaster recovery services; UAV M1for communications among rescue team members, UAV M2 as emergencyreplacements of mobile and/or fixed wireless base stations for residentcommunications via their existing mobile phones and/or personalcommunications devices using WiFi. The third UAV platform M3 performsreal time imaging and surveillances via passive optical, infrared or RFsensors. All three platforms are connected to a ground hub 110 viafeeder-links in Ku and/or Ka band spectrum. The ground hub 110 willserve as gateways and have access to terrestrial networks 101.

As a result, rescue works in a coverage area 130 will have access ofreal time imaging, and communications among co-workers and dispatchingcenters connected by the hub 110. Residents in disaster/emergencyrecovery areas 130 will also be provide with ad hoc networks ofcommunications via their own personal devices to outside world, torescue teams, and/or disaster/emergency recovery authorities.

The feeder-links of the three platforms M1, M2, and M3 are identical inKu and/or Ka bands. Only the three payloads (P/L) are different; the P/Lon the first UAV M1 enables networks for communications in public safetyspectrum among members of rescue team; the P/L on the second UAV M2 isto restore resident cell phone and/or fixed wireless communications atL/S band, and the P/L on the third UAV M3 is an real time imaging sensorfor real time surveillance.

Three independent technologies are discussed; (1) retro-directive array,(2) ground based beam forming, and (3) wavefront multiplexing anddemultiplexing (WF muxing/demuxing). Retro-directive links forfeeder-links are to make the feeder links payload on UAVs to communicatewith designated ground hubs more effectively, using less power, reachinghubs in further distances, and/or more throughputs.

The architectures of ground base beam forming (GBBF), or remote beamforming (RBF), for UAV platform base communications will support andaccomplish designed missions using P/L with smaller SW&P. Beam formingprocessing may be located remotely on ground (e.g. GBBF) or anchored onother platforms on air, on ground, or at sea. GBBF architectures areused for illustrations in here. However, similar RBF architecture can bedeveloped for the platforms which may be mobile, re-locatable, fixed,and/or combinations of all above to perform remote beam formingfunctions.

Wavefront multiplexing and demuxing techniques can be applied in manyadvanced applications for UAV based mobile communications including thefollowing three:

-   -   (1) Calibrating back channels in feeder-links    -   (2) coherent power combining of radiated power by different UAVs        in ground receivers in contracts to “spatial power combining”        using conventional array antennas;    -   (3) generating data security and redundancy in segmented data        packages for concurrent delivery through various UAVs, different        channels in a UAV, and combinations of both.

There are four technologies in this architecture:

-   -   1. UAVs 120 as communications nodes    -   2. Fore-ground communications networks between users in a        coverage area 130 and UAVs 120        -   For users with hand held devices at L/S bands        -   utilizing remote-beam forming network (RBFN) with the ground            based beam forming (GBBF) processing in a ground mobile hub            facility 110    -   3. Back-ground communications networks, (back channels or        feeder-links) between ground infrastructures/facilities 110 and        UAVs 120        -   Back-channels or feeder-links between UAVs and GBBF            processing centers via retro-directive antennas.    -   4. Wavefront multiplexing/de-multiplexing (WF muxing/demuxing);        -   Back-channel calibrations on feeder-link transmission for            RBF/GBBF        -   Coherent power combining in receivers on signals from            different channels on various UAVs;        -   Secured transmissions with redundancies via UAVs.

FIG. 2 depicts both return links and forward links of a UAV based mobilecommunications 200 with on-board beam forming network (BFN) 211 over acoverage area 130. The UAV 120 provides interconnections among users A,B, C, and C in two beams 1302 and 1303 via a communication hub 110,which is a “gateway” to terrestrial networks 101. The communication hub110 is covered by the feeder-link beam illuminated by an on-boardfeeder-line antenna 236 at Ka or Ku band. We assume these users are atL/S bands, including bands covering commercial cell phones and WiFiband.

The P/L 200 consists of three sections supporting both forward andreturn links; (1) a foreground communications payload (P/L) 210 at L/Sband, (2) frequency translation sections 220 between L/S band of andKu/Ka bands, and (3) a feeder-link payload 230 at Ku/Ka band.

Similar architectures also are applicable to other selected bandwidthsfor other foreground communications payload (P/L) 210; such as foremergency rescue workers at 4.9 GHz reserved for public safety spectrum.

A multi-beam antenna 211 with many array elements 217 in the foregroundlink payload (P/L) 210 at L/S band is used for both transmission inforward links and receptions in return links. There are at least threebeams, 1301, 1302, and 1303 over the coverage area 130. Theinputs/outputs ports to the multi-beam antenna 211 are the “beam ports”connected by diplexers 213, where the return link beam-ports areconnected to LNAs 214 at L/S band, and the forward link beam-ports areconnected to power amplifiers 215.

There are at least two pairs of frequency translation units 220. Thereturn link units feature frequency up-conversion from L/S band (1/2GHz) to Ku/Ka band (12/20 GHz) . The forward link units translatesignals at Ku/Ka band (14/30 GHz) to those at L/S band L/S band (1/2GHz).

Feeder-link P/L 230 features two groups of “beam” signals. For thereturn link signals, the muxing devices of 231 combines the beam signalsat various translated frequency slots in Ku/Ka band into a singlestream, then power amplified by a PA 235, duplexed by an antennadiplexer 233 before radiated by the feeder-link antenna 236 in afeeder-link payload (P/L) 230. Similarly for signals in forward links,the feeder-link signals received by the antenna 236 and I/O duplexer 233are conditioned by Ku/Ka band LNA 234. The Ku/Ka band demuxing devices232 separates beam signals by dividing the conditioned signals intovarious beam-ports before translating them from proper frequency slotsin Ku/Ka band into a common frequency slot in L/S band by the frequencyconverters 220. These input beam signals are power amplified byindividual power amplifiers 215 in the foreground P/L before radiated bythe foreground-link multibeam antenna 211.

We have assumed the muxing device 231 performs frequency divisionmultiplexing (FDM) and consistent with an associated device on groundperforming frequency division demultiplexing (FDM demuxing). However,the muxing/demuxing functions of 231/232 may perform via othermuxing/demuxing schemes such as time division muxing (TDM), codedivision muxing (CDM), or combinations of FDM, CDM and/or TDM.

FIG. 2 presents systems and methods to restore mobile communications forresidents in a disaster area via a small UAV M2 which features on-boardbeam forming capability and serves as a communications relay to groundgateways. As an example depicted in FIG. 2, a first user A in beam 1303is sending a data string to a fourth user D in Beam 1302, an on boardpayload (P/L) of a M2 UAV 120 will pick up the data sent by the firstuser A in Beam 1303 via the multi-beam antenna 211. The first user Awill use his/her own cell-phone or portable devices via WiFi spectrum.The received data string by the multi-beam antenna 211 will be amplifiedby a LNA 214, filtered and frequency translated by a transponder 220,power amplified 235 and then radiated by the feeder-link antenna 236 atKa or Ku band. The feeder link antennas on the M2 UAV shall be a highgain tracking beam antenna with a tracking beam always pointed to aground hub 110 as the M2 UAV 120 moves.

The on-board feeder-link antennas may also be implemented as low gainantennas including omni directional ones to simplify complexity onfeeder-link tracking mechanisms with a price of reduced channel capacityand/or operational ranges between the M2 UAV 120 and the ground hub 110.

The hub 110 will assign the received data stream to a forward link beamport, through which the data will be delivered to a desired receivinguser, the user D, in Beam 1302.

An uplink data stream in the ground facility 110 designated for aforward link beam port of the on-board BFN 211 is up-loaded via theKu/Ka band feeder-link and captured by the feeder-link antenna 236. Thecaptured signals are conditioned via a LNA and a band pass filter (BPF)before FDM demuxed to a common IF by a FDM demuxer 232. The demuxedcomponents are different beam signal streams for various input ports ofthe multibeam antenna 217.

Concurrently a third user C in beam 1302 want to send a different datastring to a second user B in Beam 1303, the on board P/L 210 will pickup the data sent by the third user C in Beam 1302 via the multi-beamantenna 211, the received data from the user C will be amplified by aLNA 214, filtered and frequency translated by one of the transponders220, power amplified 235 and then radiated by the feeder-link antenna236 at Ka or Ku band. The hub 110 will assign the received data streamto a forward link beam port, which will deliver the data to the desiredreceiving user, user B, in Beam 1303.

It is clear that there are no “switching or connecting” mechanisms atall among users over the coverage area 130 for the P/L 200 on the UAV120. The switching and connecting mechanisms are performed in the groundhub 110.

Referring to FIG. 2, the M2 UAV 120 may only provide one-way forwardcommunications such as broadcasting or multicasting. Forward links ofthe M2 UAV 120 based mobile communications with on-board beam formingnetwork (BFN) 211. The M2 UAV 120 provides interconnections to a firstreceiving mobile user B in the beam position 1303 from a communicationhub 110 connected to a first data source which may come from terrestrialnetworks 101, or via on return links of the UAV 120. The UAV 120concurrently provides interconnections to a second receiving mobile userDin the beam position 1302 from a communication hub 110 connected to asecond data source which may come from terrestrial networks 101, or viareturn links of the UAVs 120.

Referring to FIG. 2, the M2 UAV 120 may only provide one-way return link(receiving only) services including other applications such as bi-staticradar receiver functions. Return links of the M2 UAV 120 based mobilecommunications with on-board beam forming network (BFN) 211. The M2 UAV120 provides interconnections from a first data source A in the beamposition 1303 to a ground processing hub 110 connected to a first datareceiver via terrestrial networks 101, or to a data receiver in the samecoverage area 130 via forward links of the UAVs 120. Concurrently, theUAV 120 provides interconnections from a second data source C in thebeam position 1302 to a processing hub 110 which may be connected to asecond data receiver via terrestrial networks 101 or via forward linksof the UAVs 120.

FIG. 3 depicts both return links and forward links of a UAV based mobilecommunications 200 with no on-board beam forming network (BFN) 211 overa coverage area 130. The UAV 120 provides interconnections among usersA, B, C, and C in two beams 1302 and 1303 via a communication hub 110,which is a “gateway” to terrestrial networks 101. The communication hub110 is covered by the feeder-link beam illuminated by an on-boardfeeder-line antenna 236 at Ka or Ku band. We assume these users are atL/S bands, including bands covering commercial cell phones and WiFiband.

The P/L 200 consists of three sections supporting both forward andreturn links; (1) a foreground communications payload (P/L) 210 at L/Sband, (2) frequency translation sections 220 between L/S band of andKu/Ka bands, and (3) a feeder-link payload 230 at Ku/Ka band.

Similar architectures also are applicable to other selected bandwidthsfor other foreground communications payload (P/L) 210; such as foremergency rescue workers at 4.9 GHz reserved for public safety spectrum.

The on board L/S band antennas in the feeder-link payload (P/L) 230 aremany individual array elements 217 at L/S band. They are used for bothtransmission in forward links and receptions in return links. There areat least three beams, 1301, 1302, and 1303 over the coverage area 130.The inputs/outputs ports to the array elements 217 are the“element-ports” connected by diplexers 213, where the return linkelement-ports are connected to LNAs 214 at L/S band, and the forwardlink element-ports are connected to power amplifiers 215.

There are at least two pairs of frequency translation units 220. Thereturn link units feature frequency up-conversion from L/S band (1/2GHz) to Ku/Ka band (12/20 GHz). The forward link units translate signalsat Ku/Ka band (14/30 GHz) to those at L/S band L/S band (1/2 GHz).

Feeder-link P/L 230 features two groups of “element” signals. For thereturn link signals, the muxing devices of 231 combines various“element” signals at various translated frequency slots in Ku/Ka bandinto a single stream, then power amplified by a power amplifier (PA)235, duplexed by an antenna diplexer 233 before radiated by thefeeder-link antenna 236.

Similarly for signals in forward links, the feeder-link signals receivedby the antenna 236 and I/O duplexer 233 are conditioned by Ku/Ka bandLNA 234. The Ku/Ka band demuxing devices 232 separates variouselement-signals by dividing the conditioned signals into various“element-ports” before translating them from proper frequency slots inKu/Ka band into a common frequency slot in L/S band by the frequencyconverters 220. These element signals are then power amplified byindividual power amplifiers 215 in the foreground P/L 310 beforeradiated by the individual foreground-link antenna elements 217.

We have assumed the muxing device 231 performs frequency divisionmultiplexing (FDM) and consistent with an associated device on groundperforming frequency division demultiplexing (FDM demuxing). However,the muxing/demuxing functions of 231/232 may perform via othermuxing/demuxing schemes such as time division muxing (TDM), codedivision muxing (CDM), or combinations of FDM, CDM and/or TDM.

FIG. 4 depicts a scenario with a small M1 a UAV 120-1 performing acommunication relay mission via GBBF for residents in L/S bands. Theforeground links 420 feature multiple spot beams 1301, 1302, and 1303 inL/S band servicing coverage 130 with <100 Km in diameter. A ground user436 may use his/her own cell phone communicating to other users in oroutside the same coverage area 130. The coverage 130 area may varydepending on requirements on missions.

The ground hub 410 in FIG. 4 will receive and condition signals from thefeeder-link 450 in their frontend 411. A ground based beam forming(GBBF) processor 412 will (1) recover the received signals of theon-board elements 217 with precision amplitudes and phases, (2) performdigital beam forming (DBF) processing on the recovered element signalsgenerating received beam signals, and (3) deliver the received beamsignals for further receiving functions including demodulation toconvert waveforms into data strings before sending them to destinationsperformed by mobile hubs 413 via terrestrial networks 480. The detailsof GBBF for both Forward links and Return links will be descripted indetails in FIG. 12.

Similarly for signals in forward links, the ground based beam forming(GBBF) processor 412 will (1) receiving the transmitting “beam-signals”from a transmitter after functions including modulation and channelformatting performed by the mobile hubs 413 from signal sources whichmay come via terrestrial networks 480, (2) performing transmit digitalbeam forming (DBF) processing on the “beam signals” in basebandgenerating parallel element-signals in baseband to be transmitted in L/Sband by the small M1 a UAV 120-1, and (2) up-converting and FDM muxingthese element signals to Ku/Ka for uplink to the UAV 120-1 via thefeeder-link. Multiple beam-signals are designated to users in variousspot beams 1301, 1302, and 1303 over the coverage area 130. Thesetransmitted beam signals will be delivered to various users in thecoverage area 130 concurrently

Onboard the small M1 a UAV 120-1, as depict in FIG. 3, the up-linkedsignals received by the feeder antenna 236 and I/O duplexer 233 areconditioned by Ku/Ka band LNA 234. The Ku/Ka band demuxing devices 232separates “element” signals by dividing the conditioned signals toelement various ports before translating them from proper frequencyslots in Ku/Ka band into a common frequency slot in L/S band by thefrequency converters 220. These input beam signals are power amplifiedby individual power amplifiers 215 in the foreground P/L before radiatedby the foreground-link array elements 217.

We have assumed the muxing device 231 performs frequency divisionmultiplexing (FDM) and consistent with an associated device on groundperforming demuxing of FDM. However, muxing/demuxing device 231/232 mayperform other muxing/demuxing schemes such as time division muxing(TDM), code division muxing CDM, or combinations of TDM, CDM and/or FDM.

Embodiment 1

FIG. 3 presents an example of systems and methods to restore mobilecommunications for residents in a disaster area via a small UAV M2 whichfeatures ground based beam forming (GBBF) or remote beam-forming network(RBFN) capability and serves as a communications relay to groundgateways. Referring to FIG. 3, the M2 UAV 120 may only provide one-wayforward communications such as broadcasting or multicasting. Forwardlinks of the M2 UAV 120 based mobile communications with on-board arrayelements 217 but no beam forming functions at all. The M2 UAV 120provides interconnections to a first receiving mobile user B in the beamposition 1303 from a communication hub 110 after GBBF functions 1101connected to a first data source which may come from terrestrialnetworks 101, or via on return links of the UAV 120. The UAV 120concurrently provides interconnections to a second receiving mobile userD in the beam position 1302 from a communication hub 110 connected to asecond data source which may come from terrestrial networks 101, or froma source in the same coverage area 130 via return links of the UAVs 120.The processing/communication hub 101 will also perform transmittingbeam-forming functions concurrently for many transmit beams for thearray elements on the M2 UAV.

Referring to FIG. 3, the M2 UAV 120 may only provide one-way return link(receiving only) services including bi-static radar receiver functions.Return links of the M2 UAV 120 based mobile communications with on-boardarray elements 217 but without beam forming network (BFN). The M2 UAV120 provides interconnections to a first data source A in the beamposition 1303 to a ground processing hub 110 connected to a first datareceiver via terrestrial networks 101, or via forward links of UAVs 120to a user in the UAV coverage area 130. Concurrently, the UAV 120provides interconnections to a second data source C in the beam position1302 to a processing hub 110 which may be connected to a second datareceiver via terrestrial networks 101 or a receiver in the same coveragearea 130 via forward links of the UAVs 120. The M2 UAV 120 providesinterconnections from residents in the coverage area 130 to acommunication hub which shall serve as “gateways” to terrestrialnetworks. The processing/communication hub 101 will perform receivingbeam-forming functions concurrently for many receiving beams for thearray elements on the M2 UAV.

FIG. 4 depicts a similar embodiment via a M1 UAV 120-1 forcommunications mainly to rescue worker community in a coverage area 130.The ground facility 410 features:

-   -   1. multiple beam antennas 411 to connected to various UAV        platforms 120 concurrently via different Ku/Ka band feeder-links        450,    -   2. GBBF for both forward link (transmitting) beams and return        link (receiving) beams    -   3. mobile hubs 413 as gateways to terrestrial networks 480 or        other UAV based networks.

The M1 a UAV 120-1 along with its GBBF processing features multiplebeams 1301, 1302, 1303, and etc. in both forward and return links in areserved public safety frequency band; e.g. 4.9 GHz or 700 MHz in US.The users (rescue worker community) in the coverage areas feature omnidirectional terminals 436

FIG. 4 presents an example of systems and methods for broadcastingand/or multicasting via a small UAV with GBBF or RBFN. One-waycommunications are depicted, transmitting to rescue worker community ina coverage area 130 via a M1 UAV 120-1. The ground facility 410features:

-   -   1. multiple beam antennas 411 support a Ku/Ka band feeder-link        450 from the ground facility 410 to the M1 a UAV 120-1 platform,    -   2. GBBF processing including beam forming functions for        concurrent forward link (transmitting) multiple beams    -   3. mobile hubs 413 as gateways to terrestrial networks 480 or        other UAV based networks.

The M1 a UAV 120-1 along with its GBBF processing features multiple Txbeams 1301, 1302, 1303, and etc. including forward links in a reservedpublic safety frequency band; eg. 4.9 GHz or 700 MHz in US.

The users (rescue worker community) in the coverage areas shall featureomni directional terminals 436.

The M1 a UAV 120-1 provides interconnections from mobile users to acommunication hub connected to terrestrial networks.

This embodiment can be used as platforms for bi-static radar receivers.The associated processing facility 411 on ground may be modified toperform not only functions of beam forming via GBBF 412, but also signalprocessing functions of range gating, Doppler frequency separations, aswell as additional radar/imaging processing.

FIG. 5 depicts a scenario with 4 small UAVs 520-1 performing acommunication relay mission via GBBF for residents in L/S bands. Thefour small UAVs 520-1 identified as M1 a, M1 b, M1 c and M1 d are flyingin formations closely spaced among one another (say, 10 m or less). Theforeground links 420 feature multiple spot beams 1301, 1302, and 1303 inL/S band servicing coverage 130 with <100 Km in diameter. A ground user436 may use his or her own cell phone communicating to other users in oroutside the same coverage area 130. The coverage 130 may vary dependingon requirements on missions.

The ground hub 410 in FIG. 4 will receive and condition signals in thefeeder-links 550 in their frontend 411. A ground based beam forming(GBBF) processor 412 will (1) recover the received signals of theon-board elements 217 from all 4 small UAVs 520-1 with precisionamplitudes and phases, (2) perform digital beam forming (DBF) processingon the recovered element signals from various UAVs 520-1 generatingreceived beam signals, and (3) deliver the received beam signals forfurther receiving functions including demodulation to convert waveformsinto data strings before sending them to destinations performed bymobile hubs 413 via terrestrial networks 480. The details of GBBF forboth Forward links and Return links will be descripted in details inFIG. 12.

Similarly for signals in forward links, the ground based beam forming(GBBF) processor 412 will (1) receiving the transmitting “beam-signals”from a transmitter after functions including modulation and channelformatting performed by the mobile hubs 413 from signal sources whichmay come via terrestrial networks 480, (2) performing transmit digitalbeam forming (DBF) processing on the “beam signals” in basebandgenerating parallel element-signals in baseband to be transmitted in L/Sband by the four small UAVs 520-1 concurrently, and (2) up-convertingand FDM muxing these element signals to Ku/Ka for uplinks to the 4 smallUAV 520-1 via the feeder-links 550. Multiple beam-signals are designatedto users in various spot beams 1301, 1302, and 1303 over the coveragearea 130. These transmitted beam signals will be delivered to varioususers in the coverage area 130 concurrently

Onboard each of the 4 small UAV 520-1, the processing from feeder-linkto foreground links are identical. In the M1 a UAV 120-1 shown in FIG. 3as an example, the up-linked signals received by the feeder antenna 236and I/O duplexer 233 are conditioned by Ku/Ka band LNA 234. The Ku/Kaband demuxing devices 232 separates “element” signals by dividing theconditioned signals to various element ports before translating themfrom proper frequency slots in Ku/Ka band into a common frequency slotin L/S band by the frequency converters 220. These input beam signalsare power amplified by individual power amplifiers 215 in the foregroundP/L before radiated by the foreground-link array elements 217.

We have assumed the muxing device 231 performs frequency divisionmultiplexing (FDM) and consistent with an associated device on groundperforming demuxing of FDM. However, muxing/demuxing device 231/232 mayperform other muxing/demuxing schemes such as time division muxing(TDM), code division muxing CDM, or combinations of TDM, CDM and/or FDM.

Another example presents systems and methods of implementing ad hocmobile communications for rescued workers in a disaster area viamultiple closely spaced small UAVs featuring GBBF or RBFN. The term “M1UAVs 520-1 ” is used to represent all 4 small UAVs; the M1 a UAV, the M1b UAV, the M1 c UAV, and the M1 d UAV in FIG. 5. FIG. 5 depicts anembodiment via multiple M1 UAVs 520-1 for communications mainly torescue worker community in a coverage area 130.

The ground facility 410 features:

-   -   1. multiple beam antennas 411 to connected to various UAV        platforms 520-1 concurrently via different Ku/Ka band        feeder-links 550,    -   2. GBBF for both forward link (transmitting) beams and return        link (receiving) beams    -   3. mobile hubs 413 as gateways to terrestrial networks 480 or        other UAV based networks.

The M1 a, M1 b, M1 c, and M1 d UAVs 520-1 along with their GBBFprocessing feature multiple beams 1301, 1302, 1303, and etc. in bothforward and return links in a reserved public safety frequency band; e.g. 4.9 GHz or 700 MHz in US. The users (rescue worker community) in thecoverage areas shall feature omni directional terminals 436.

In a first operational scenario of both forward and return links ofmobile communications via multiple closely space M1 UAVs 520-1 withground based beam forming (GBBF) 412 or remote beam forming network(RBFN) via beam-forming among elements of arrays on a UAV. Ku/Kachannels in the feeder links 550 shall be designed with adequateinstantaneous bandwidths to support all UAVs concurrently. Thesetechniques may include advance multi-beam antennas for the feeder-linksin ground facility providing orthogonal beams concurrently connecting toall UAV facilitating frequency reuse. On the other hand for theforeground communications P/Ls, various UAVs provide different groups ofbeams operated at various frequency slots, different groups of codes,and/or time slots. Each supports an independent data stream. Therelative positions among arrays on different UAVs become less important.Radiated RF powers associated with many of these independent datastreams among various UAVs are not combined. Information or data streamsmay be combined for high data rate users via channel bonding.

In a second operational scenario of both forward and return links ofmobile communications via multiple closely space M1 UAVs 520-1 withground based beam forming (GBBF) 412 or remote beam forming network(RBFN) via beam-forming among distributed subarrays; each of which is ona separated UAV. Ku/Ka channels in the feeder links 550 shall bedesigned with adequate instantaneous bandwidths to support all UAVsconcurrently. These techniques may include advance multi-beam antennasfor the feeder-links in ground facility providing orthogonal beamsconnecting to all UAV concurrently facilitating frequency reuse. Thespacing among the M1 UAVs 520-1 shall vary slowly. As a result, therelative geometries among elements in this distributed and slow-varyingarray are very important in maintaining coherency among subarrays. Theslow varying array geometries must be continuously calibrated and thencompensated for both forward links and return links properly as a partof GBBF functions 412. This operation scenario will allow coherentlyadded stronger radiated signals from multiple M1 UAVs 520-1 to “punchthrough” debris or man-made structures reaching users with disadvantageterminals or at disadvantaged locations.

Another example presents systems and methods of implementing one waybroadcasting or multicasting communications via multiple closely spacedsmall UAVs featuring GBBF or RBFN. We shall use the term “M1 UAVs 520-1”to represent all 4 small UAVs; the M1 a UAV, the M1 b UAV, the M1 c UAV,and the M1 d UAV in FIG. 5. Forward links of the M1 UAVs 520-1 basedmobile communications with on-board array elements 217 but no beamforming functions at all. The M1 UAVs 520-1 provide interconnections toa first receiving mobile user B in the beam position 1303 from acommunication hub 410 after GBBF functions 412 connected to a first datasource which may come from terrestrial networks 408, or via on returnlinks of the M1 UAVs 520-1. The M1 UAVs 520-1 concurrently providesinterconnections to a second receiving mobile user D in the beamposition 1302 from a communication hub 410 connected to a second datasource which may come from terrestrial networks 408, or from a source inthe same coverage area 130 via return links of the M1 UAVs 520-1. Theprocessing/communication hub 410 will also perform transmittingbeam-forming functions concurrently for many transmit beams for thearray elements on the M1 UAVs 520-1.

In a first operational scenario of forward links of mobilecommunications via multiple closely space M1 UAVs 520-1 with groundbased beam forming (GBBF) 412 or remote beam forming network (RBFN) viabeam-forming among elements of arrays on a UAV. Ku/Ka channels in thefeeder links 550 shall be designed with adequate instantaneousbandwidths to support all UAVs concurrently. These techniques mayinclude advance multi-beam antennas for the feeder-links in groundfacility providing orthogonal beams connecting to all UAV concurrentlyfacilitating frequency reuse. Various UAVs will provide different groupsof beams operated at various frequency slots, different groups of codes,and/or time slots for the foreground communications payloads. Each UAVsupports independent data streams. The relative positions among arrayson different UAVs become less important. Radiated RF powers associatedwith many of these independent data streams among various UAVs are not“coherently combined”. Information or data streams may be combined forhigh data rate signal streams via channel bonding.

In a second operational scenario of forward links of mobilecommunications via multiple closely space M1 UAVs 520-1 with groundbased beam forming (GBBF) 412 or remote beam forming network (RBFN) viaadditional beam-forming processing among distributed subarrays; each ofwhich is on a separated UAV. Ku/Ka channels in the feeder links 550shall be designed with adequate instantaneous bandwidths to support allUAVs concurrently. These techniques may include advance multi-beamantennas for the feeder-links in ground facility providing orthogonalbeams connecting to all UAV concurrently facilitating frequency reuse.The spacing among the M1 UAVs 520-1 shall vary slowly. As a result, therelative geometries among elements in this distributed and slow-varyingarray are very important in maintaining coherency among subarrays. Theslow varying array geometries must be continuously calibrated and thencompensated for both forward links and return links properly as a partof GBBF functions 412. This operation scenario will allow coherentlyadded stronger radiated signals from multiple M1 UAVs 520-1 to “punchthrough” debris or man-made structures reaching users with disadvantageterminals or at disadvantaged locations.

Another example presents systems and methods of implementing one wayreceive only communications via multiple closely spaced small UAVsfeaturing GBBF or RBFN.

We shall use the term “M1 UAVs 520-1” to represent all 4 small UAVs; theM1 a UAV, the M1 b UAV, the M1 c UAV, and the M1 d UAV in FIG. 5.

Referring to FIG. 5, the M1 UAVs 520-1 may only provide one-way returnlink (receiving only) services including applications of bi-static radarreceiver functions. Return links of the M1 UAVs 520-1 based mobilecommunications with on-board array elements 217 similar to the one shownin FIG. 3. The M1 UAVs 520-1 provide interconnections to a first datasource A in the beam position 1303 to a ground processing hub 410connected to a first data receiver via terrestrial networks 480, or viaforward links of M1 UAVs 520-1 to a user in the coverage area 130.Concurrently, the M1 UAVs 520-1 provide interconnections to a seconddata source C in the beam position 1302 to a processing hub 410 whichmay be connected to a second data receiver via terrestrial networks 480or a receiver in the same coverage area 130 via forward links of the M1UAVs 520-1. The M1 UAVs 520-1 provide interconnections from data sourcesin the coverage area 130 to a communication hub which shall serve as“gateways” to terrestrial networks. The processing/communication hub 410will perform receiving beam-forming functions concurrently for manyreceiving beams for the array elements on the multiple M1 UAVs 520-1.

In a first operational scenario of return links of mobile communicationsvia multiple closely space M1 UAVs 520-1 with ground based beam forming(GBBF) 412 or remote beam forming network (RBFN) via beam-forming amongelements of arrays on a UAV. Ku/Ka channels in the feeder links 550shall be designed with adequate instantaneous bandwidths to support allUAVs concurrently. These techniques may include advance multi-beamantennas for the feeder-links in ground facility providing orthogonalbeams connecting to all UAV concurrently facilitating frequency reuse.Various UAVs provide different groups of beams operated at variousfrequency slots, different groups of codes, and/or time slots. Eachsupports an independent data stream. The relative positions among arrayson different UAVs become less important. Received RF powers associatedwith many of these independent data streams among various UAVs are not“coherently” combined. Information or data streams may be combined forhigh data rate users via channel bonding.

In a second operational scenario of return links of mobilecommunications via multiple closely space M1 UAVs 520-1 with groundbased beam forming (GBBF) 412 or remote beam forming network (RBFN) viabeam-forming among distributed subarrays; each of which is on aseparated UAV. Ku/Ka channels in the feeder links 550 shall be designedwith adequate instantaneous bandwidths to support all UAVs concurrently.These techniques may include advance multi-beam antennas for thefeeder-links in ground facility providing orthogonal beams connecting toall UAV concurrently facilitating frequency reuse.

The spacing among the M1 UAVs 520-1 shall vary slowly. As a result, therelative geometries among elements in this distributed and slow-varyingarray are very important in maintaining coherency among subarrays. Theslow varying array geometries must be continuously calibrated and thenproperly compensated for return links as a part of GBBF functions 412.This operation scenario will allow coherently added received signalscaptured by multiple M1 UAVs 520-1 to enhance received signal-to-noiseratio (SNR).

In addition, multibeam GNSS receivers [1, 2, 3] on individual UAVs shallprovide current status on information not only for the individualplatform positions but also for the platform orientations. Thus allelement current positions and orientations of a subarray on a moving UAVcan then be precisely calculated in a dynamic coordinate moving with themean velocity of all participating UAVs. Thus the geometry of a dynamicarray distributed among multiple slow moving UAVs can then be calculatedprecisely for a current flying trajectory position, and may also beprojected for next few flying trajectory positions a few seconds ahead.

In bi-static radar receiving applications, coherent combining ofcaptured signal returns among multiple UAVs will provide enhanced SNRand also better spatial resolutions. RF illuminators for these bi-staticor multi-static radars may be many of the GNSS satellites at L-band forglobal coverage, C-band satellites for land and ocean coverage, or Kuand Ka band high power DBS satellites or spot beam satellites for manyland mass coverage or near equatorial coverage on land mass, on oceanand in air services.

FIG. 6 depicts a scenario with 4 small UAVs 620-1 performing acommunication relay mission via GBBF for residents in L/S bands. Thefour small UAVs 620-1 a, 620-1 b, 620-1 c and 620-1 d identified as M1a, M1 b, M1 c and M1 d are distributed in a fly formation with largedistances among them (say, >1 Km). The foreground links 420 of each ofthe 4 UAVs feature multiple spot beams 1301, 1302, and 1303 in L/S bandservicing coverage 130 with <100 Km in diameter. A ground user 436 mayuse an advanced user device communicating to other users in or outsidethe same coverage area 130. The advanced user device features multipletracking beams at concurrently and independently following all 4 smallUAVs. The multiple-beams of an advanced user terminals operate at samefrequency slots among the links between each of the four UAVs and theground user. The coverage 130 area may vary depending on requirements onmissions.

The ground hub 410 in FIG. 6 will receive and condition signals from the4 UAVs (M1 a 620-1 a, M1 b 620-1 b, M1 c 620-1 c, and M1 d 620-1 d) viathe 4 separated feeder-links 550 at its frontend 411. A ground basedbeam forming (GBBF) processor 412 will (1) recover the received signalsof the on-board elements 217 from all 4 small UAVs 620-1 a, 620-1 b,620-1 c, and 620-1 d with precision amplitudes and phases, (2)concurrently perform 4 sets of digital beam forming (DBF) processing onthe recovered element signals from 4 UAVs 620-1 generating 4 concurrentreceiving beam signals for each ground user, and (3) deliver the 4received beam signals for further receiving functions includingdemodulation to convert waveforms into data strings, (4) channel-bondingof received signals to form a string of the received beam signals fromone user but through 4 different UAV's before sending them todestinations performed by mobile hubs 413 via terrestrial networks 480.The sequence of the processing in (3) and (4) may be reversed if signalmodulations in all 4 feeder-links are identical. The details of GBBF forboth Forward links and Return links will be descripted in details inFIG. 12.

Similarly for signals in forward links, the ground based beam forming(GBBF) processor 412 will (1) receiving the transmitting “beam-signals”from a transmitter after functions including modulation and channelformatting performed by the mobile hubs 413 from signal sources whichmay come via terrestrial networks 480, (2) segmenting the modulatedsignals into 4 substream beam signals (2) performing 4 concurrent butindependent transmit digital beam forming (DBF) processing on each ofthe “substream beam signals” in baseband generating parallelelement-signals in baseband to be transmitted in L/S band by the foursmall UAVs 620-1 concurrently, and (2) up-converting and FDM muxingthese element signals to Ku/Ka for uplinks to the 4 small UAV 620-1viathe feeder-links 550. Multiple beam-signals are designated to users invarious spot beams 1301, 1302, and 1303 from 4 separated UAV over thesame coverage area 130. These transmitted beam signals will be deliveredto various users in the coverage area 130 concurrently. The user with anadvanced multi-beam terminal will have an advantage of 4 times thechannel capacity as compared to the capacity from a single UAV 120

Onboard each of the 4 small UAV 620-1, the processing from feeder-linkto foreground links are identical. Taking that of the M1 a UAV 120-1shown in FIG. 3 as an example, the up-linked signals received by thefeeder antenna 236 and I/O duplexer 233 are conditioned by Ku/Ka bandLNA 234. The Ku/Ka band demuxing devices 232 separates “element” signalsby dividing the conditioned signals to various element ports beforetranslating them from proper frequency slots in Ku/Ka band into a commonfrequency slot in L/S band by the frequency converters 220. These inputbeam signals are power amplified by individual power amplifiers 215 inthe foreground P/L before radiated by the foreground-link array elements217.

We have assumed the muxing device 231 performs frequency divisionmultiplexing (FDM) and consistent with an associated device on groundperforming demuxing of FDM. However, muxing/demuxing device 231/232 mayperform other muxing/demuxing schemes such as time division muxing(TDM), code division muxing CDM, or combinations of TDM, CDM and/or FDM.

Next example presents systems and methods of implementing ad hoc mobilecommunications for rescued workers in a disaster area via largely spacedmultiple small UAVs featuring GBBF or RBFN. The rescued workers shall beequipped with multiple beam terminals.

The term “M1 UAVs 620-1” is used to represent all 4 small UAVs; the M1 aUAV 620-1 a, the M1 b UAV 620-1 b, the M1 c UAV 620-1 c, and the M1 dUAV 620-1 d in FIG. 6. FIG. 6 depicts an embodiment via multiple M1 UAVs620-1 for communications mainly to rescue worker community in a coveragearea 130.

The ground facility 410 features:

-   -   1. multiple beam antennas 411 to connected to various UAV        platforms 620-1 concurrently via different Ku/Ka band        feeder-links 550,    -   2. GBBF for both forward link (transmitting) beams and return        link (receiving) beams    -   3. mobile hubs 413 as gateways to terrestrial networks 480 or        other UAV based networks.

The M1 a, M1 b, M1 c, and M1 d UAVs 620-1 along with their GBBFprocessing feature multiple beams 1301, 1302, 1303, and etc. in bothforward and return links in a reserved public safety frequency band; eg.4.9 GHz or 700 MHz in US.

The users (rescue worker community) in the coverage areas shall featuremultiple tracking-beam terminals 633. Each of the advanced userterminals exhibits capability of tracking the 4 M1 UAVs 620-1 with fourseparated beams operating at the same frequency slots in a reservedpublic safety band concurrently. Goode isolations among multiple UAVsoperating at same frequency bandwidths, codes and time slots areachieved via spatial isolations from the advanced user terminals. As aresult, same spectrum is used 4 times more than the scenarios presentedin FIG. 5.

In a first operational scenario of both forward and return links ofmobile communications via multiple closely space M1 UAVs 520-1 withground based beam forming (GBBF) 412 or remote beam forming network(RBFN) via beam-forming among elements of arrays on a UAV. Ku/Kachannels in the feeder links 550 shall be designed with adequateinstantaneous bandwidths to support all M1 UAVs 620-1 concurrently.These techniques may include advance multi-beam antennas for thefeeder-links in ground facility 410 providing orthogonal beamsconcurrently connecting to all UAV facilitating frequency reuse.Similarly for the foreground communications P/Ls, various UAVs providedifferent groups of beams operated at same frequency slots supportingindependent data streams. The relative positions among arrays ondifferent UAVs become less important. Radiated RF powers associated withmany of these independent data streams among various UAVs are notcombined. Information or data streams may be combined for high data rateusers via channel bonding.

In a second operational scenario of both forward and return links ofmobile communications via multiple closely space M1 UAVs 520-1 withground based beam forming (GBBF) 412 or remote beam forming network(RBFN) via beam-forming among distributed subarrays; each of which is ona separated UAV. Ku/Ka channels in the feeder links 550 shall bedesigned with adequate instantaneous bandwidths to support all UAVsconcurrently. These techniques may include advance multi-beam antennasfor the feeder-links in ground facility providing orthogonal beamsconnecting to all UAV concurrently facilitating frequency reuse. Thespacing among the M1 UAVs 520-1 shall vary slowly. As a result, therelative geometries among elements in this distributed and slow-varyingarray are very important in maintaining coherency among subarrays. Theslow varying array geometries must be continuously calibrated and thenproperly compensated for both forward links and return links as a partof GBBF functions 412. This operation scenario will allow coherentlyadded stronger radiated signals from multiple M1 UAVs 520-1 to “punchthrough” debris or man-made structures reaching users with disadvantageterminals or at disadvantaged locations.

However, this group of operational scenarios which exhibit coherentcombining via Tx DBF in GBBF among multiple moving UAV platforms 620-1is very difficult and thus less cost-effective to implement due todynamic path length calibration and compensations among paths viadifferent UAVs.

We will introduce wave-front multiplexing/demultiplexing (WFmuxing/demuxing) techniques for path length calibrations andcompensations in Embodiment 10.

FIG. 7 depicts a scenario with 4 small UAVs 620-1 performing acommunication relay mission via GBBF for residents in L/S bands over anemergency coverage 130. The four small UAVs 620-1 a, 620-1 b, 620-1 cand 620-1 d identified as M1 a, M1 b, M1 c and M1 d are distributed in afly formation with large distances among them (say, >1 Km). WF muxingand demuxing techniques are utilized in this configuration to performcoherent power combining of radiated signals by the four small UAVs inadvanced receivers. The ground hub 710 comprises 4 separated feeder-linktracking antennas 411 at KU/Ka bands, continuously tracking 4 differentUAVs 620-1 a, 620-1 b, 620-1 c, and 620-1 d. These four separatedantennas 411 could be replaced by one multi-beam antenna with largeinstantaneous FOV to track 4 airborne platforms continuously

The foreground links 420 of each of the 4 UAVs feature multiple spotbeams 1301, 1302, and 1303 in L/S band servicing a coverage 130 with<100 Km in diameter. A ground user 633 may use an advanced user devicecommunicating to other users in or outside the same coverage area 130.The advanced user device 633 features multiple tracking beams atconcurrently and independently following all 4 small UAVs 620-1. Themultiple-beams of an advanced user terminal operate at same frequencyslots among the links between each of the four UAVs 620-1 and the grounduser 633. The coverage 130 area may vary depending on requirements onmissions.

Onboard each of the 4 small UAV 620-1, the processing from feeder-linkto foreground links are identical. Taking that of the Mla UAV 120-1shown in FIG. 3 as an example, the up-linked signals received by thefeeder antenna 236 and I/O duplexer 233 are conditioned by Ku/Ka bandLNA 234. The Ku/Ka band demuxing devices 232 separates “element” signalsby dividing the conditioned signals to various element ports beforetranslating them from proper frequency slots in Ku/Ka band into a commonfrequency slot in L/S band by the frequency converters 220. These inputbeam signals are power amplified by individual power amplifiers 215 inthe foreground P/L before radiated by the foreground-link array elements217.

We have assumed the muxing device 231 perform frequency divisionmultiplexing (FDM) and consistent with an associated device on groundperforming demuxing of FDM. However, muxing/demuxing device 231/232 mayperform other muxing/demuxing schemes such as time division muxing(TDM), code division muxing CDM, or combinations of TDM, CDM and/or FDM.

FIG. 7A depicts a more detailed flow diagram for a forward linktransmissions with WF muxing 714 co-located with a GBBF 412 groundfacility and WF demuxing 724 in an advanced user terminal 633.

We follow the following notations:

-   -   (1) for a WF muxing device        -   a. Input ports are referred as “slices”:            -   First input port of the WF muxer is referred to as                “slice 1”;        -   b. Outputs are called “wave-front components” or “wfcs”:            -   First output port of the WF muxer is referred to as “wfc                1”.    -   (2) Similarly, for a WF demuxing device        -   a. Output ports are referred as “slices”:            -   First output port of the WF demuxer is referred to as                “slice 1”;        -   b. Inputs are called “wave-front components” or “wfcs”:            -   First input port of the WF demuxer is referred to as                “wfc 1”.

In the forward link depicted in FIG. 7A from a ground hub 710 to a user633 through 4 UAVs 620-1, WF muxing are utilized to transform a firstuser input, S1, and a probing/diagnostic signal, p1, by a 4-to-4 WFmuxer 712 into 4 WF domain signals. S1 connected to slice 1 isdesignated to be sent to the user terminal 633 in the beam position1302. Two other signals connected to slice 2 and slice 3 respectively,S2 and S3, are concurrently transmitted through the same 4 UAVs via WFmuxing processing. They are intended for other users in the same spotbeam 1302. The diagnostic stream, p1, is connected to slice 4.

A WF muxing device may be implemented in many ways including a FFT, aHadamard matrix in digital formats, or combinations of FFT and Hadamardmatrixes. It may also be constructed by a Butler Matrix (BM) in analoguepassive circuitry. In FIG. 7a , the 4-to-4 WF muxer 712 in the WFmuxing/demuxing process facility 714 feature 3 user signal inputsconnected to 3 input slices (S1, S2, and S3), and a stream of pilotcodes, ps, to the 4^(th) input slice.

-   -   1. The outputs of the WF muxer 712 are various summations of 4        weighted inputs; s1, s2, s3, and ps. Specifically , y1, y2, y3,        and y4 are respectively formulated as:

y1(t)=w11*s1(t)+w12*s2(t)+w13*s3(t)+w14*ps(t)   (1.1)

y2(t)=w21*s1(t)+w22*s2(t)+w23*s3(t)+w24*ps(t)   (1.2)

y3(t)=w31*s1(t)+w32*s2(t)+w33*s3(t)+w34*ps(t)   (1.3)

y4(t)=w41*s1(t)+w42*s2(t)+w43*s3(t)+w44*ps(t)   (1.4)

-   -   -   where, s1(t)=S1, s2(t)=S2, s3(t)=S3, and s4(t)=S4.

    -   2. A wavefront vector (WFV) featuring 4 WF components (wfc) is        defined as a column matrix. There are four such vectors (column        matrixes) which are mutually orthogonal:

WFV1=WF1=Transport of [w11, w21, w31, w41]   (2.1)

WFV2=WF2=Transport of [w12, w22, w32, w42]   (2.2)

WFV3=WF3=Transport of [w13, w23, w33, w43]   (2.3)

WFV4=WF4=Transport of [w14, w24, w34, w44]   (2.4)

-   -   3. WFX*WFY=1 if X=Y, otherwise WFX*WFY=0; where X and Y are        integers from 1 to 4.    -   4. s1(t), s2(t), s3(t), and ps(t) are, respectively, “attached”        to one of the 4 WF vectors by connecting to a corresponding        input port of the WF muxing device 714.        -   (1) The outputs y1(t), y2(t), y3(t), and y4(t) are linear            combinations of wavefront components (wfcs); the aggregated            data streams. The signal stream y1 is the output from the            output port wfc-1, y2 from wfc-2, and so on.        -   (2) The S1 signal is replicated and appears in all 4 wfc            output ports. Actually, S1 is “riding on the WF vector WF1.            So are the S2, S3, and ps signals.        -   (3) The 4 outputs, y1, y2, y3, and y4 are connected to            inputs of 4 separated transmit (Tx) digital beam forming            (DBF) processors 751, converting them as parts of 4 sets of            element signals for arrays on various UAVs. Assuming Ne            array elements for the L/S band foreground communications on            each UAV 620-1, a Tx DBF processor 751 shall features Ne            element outputs        -   (4) Each of the four FDM muxers 752 performs multiplexing on            Ne corresponding element signals into a single signal            stream, which is frequency up converted and power amplified            by a set of RF front end 753 before up-loaded by one of the            4 separated high gain antennas 411 to a designated UAVs            620-1.        -   (5) GBBF 412 features 4 sets of multibeam DBF processors            751; each is designated to “service” Ne elements of the            array for foreground communications in L/S band. The4            separated arrays on 4 UAVs for foreground communications            will concurrently form L/S band beams pointed to the same            beam position 1302. As a result, y1 is delivered to the user            terminal 633 via the first UAV 620-1 a, y2 via the second            UAV 620-1 b, y3 by the third UAV 620-1 c, and y4 through the            4^(th) UAV 620-1 d.        -   (6) From the point of view of a first user who “owns” the S1            signal stream, the S1 signal stream is relayed to the            designated user terminal 633 concurrently by 4 separated            UAVs 620-1 through a common frequency slot f1.        -   (7) From the point of view of a second user who “owns” the            S2 signal stream, S2 signal is relayed to the second user            concurrently by the 4 separated UAVs 620-1 through a common            frequency slot f1. The second user is collocated in the same            beam position 1302 as that of the first user with the            terminal 633.        -   (8) From the point of view of a third user who “owns” the S3            signal stream, S3 signal is relayed to the third user            concurrently by the 4 separated UAVs 620-1 through a common            frequency slot f1. The third user is also collocated in the            same beam position 1302 as that of the first user with the            terminal 633.

These WF domain signals are inputs to four parallel DBF processors 751in a GBBF facility 710. On the other hand, a multi-beam user receiver633 features a WF demuxer which will equalize propagation paths enablingthe forward link signals which pass through 4 parallel bent-pipe pathsincluding associated electronics with unbalanced phases and amplitudedifferentials in the uploading ground segment, airborne segment, andground receiving segment. The four parallel signal paths comprise ofpropagation segments of (1) 450 a+420 a, (2) 450 b+420 b, (3) 450 c+420c, and (4) 450 d+420 d. The “bent-pipe functions” are performed by thefour UAVs M1 a 620-1 a, M1 b 620-1 b, M1 c 620-1 c, and M1 d 620-1 d.

Each bent-pipe* functions associated with each UAV 620-1 consist of:

-   -   1. receiving array element signals originated from ground        processing facility 710 via feeder-link 450,    -   2. amplifying and filtering received element signals, or        conditioning received element signals,    -   3. frequency-translating, or transponding the conditioned        element signals,    -   4. power-amplifying before re-radiating the transponded element        signals by designated array elements toward ground.

The descriptions of “bent-pipe” are to present repeater or transponderfunctions for signals going through without any regeneration process.These signals may be amplified, filtered, and/or frequency translated. Aregeneration process shall include a function of demodulation, andanother function of re-modulation.

At a destination, there are 3 functional blocks in the advanced terminal633;

-   1. Signals transponded by the four UAVs 620-1 are captured and    amplified by a multibeam receiving (Rx) array 745. The Rx array    comprises of M array elements 722, each followed by a LNA and    frequency down converter 721 for conditioning received signals.-   2. The M parallel conditioned received signals are sent to a    multibeam beam forming network (BFN) 723 which forms multiple    tracking beams following the dynamics of the relaying UAVs 620-1.    The outputs of the multi-beam BFN 723 are 4 received data streams,    y1′, y2′, y3′, and y4′, which are mainly the corresponding signals    of y1, y2, y2, and y4 contaminated by additional noises and external    interferences.-   3. A WF demux processing 724 consists of a bank of adaptive    equalizers 741 and a 4-to-4 WF demuxer 742 to reconstitute the 3    slices of signal streams and a stream of pilot codes;    -   (1) The inputs y1′, y2′, y3′, and y4′ are connected to 4        adaptive finite-impulse-response (FIR) filters 741 for time,        phase, and amplitude equalizations among the 4 propagation        paths;    -   (2) Individual adaptive filters 741 compensate for phase        differentials caused by “dispersions” among the propagation        paths (array elements) via a UAV. There will be significant        improvement on waveform shape distortions due to dispersions;        minimizing a source for inter-symbol interferences.    -   (3) Differences among 4 FIR filters 741 are optimized as a group        to compensate for time and phase differentials among propagating        paths via 4 different UAVs 620-1    -   (4) weightings of the FIR filters 741 are optimized by an        iterative control loop based on comparisons 744 of recovered        pilot signals S4 against the injected and known diagnostic        signals and an efficient optimization algorithm in an        optimization processing 743.    -   (5) the filtered outputs from the adaptive FIR filters are        connected to the WF demuxer.    -   (6) Among the outputs of the WF demuxer are the 3 slices of        desired signal streams, and a pilot signal.        -   i. The WF muxer for the first user is customized to receive            signals from the first slice, or the 1^(st) output port.        -   ii. Similarly, the WF muxer for the second user and the            third user are, respectively, customized to receive signals            from the second slice (the 2^(nd) output port) or signals            from the third slice (the 3^(rd) output port).    -   (7) The optimization loop utilizing cost minimization criteria        in the optimization processing 743 comprises:        -   i. Identifying proper observables for the optimization loop            including:            -   differences between the recovered pilot signal stream                and the original;            -   correlations of signals from output slices of the WF                demuxer 742.        -   ii. Generating different cost functions based on various            observables            -   Converting or mapping various observables into different                measurables or cost functions which must be positively                defined.                -   When an observable meets the desired performance,                    the corresponding measurable or cost function                    becomes zero.                -   When an observable is only slightly away from the                    desired performance, the corresponding measurable or                    cost function is assigned with a small positive                    number.                -   When an observable is far away from the desired                    performance, the corresponding measurable or cost                    function is assigned with a large positive number.        -   iii. Summing all cost function for a total cost as a            numerical indicator the current status of the optimization            loop performances,            -   When total cost is less than a small positive threshold                value, stop the optimization loop;            -   otherwise proceed to procedure 4        -   iv. Deriving the gradients of total cost with respect to the            weights of the adaptive equalizers which are in the forms of            FIR filters.        -   v. Calculating new weights of the FIR filters based on a            steepest descent algorithm to minimize the total cost of the            optimization loop iteratively.        -   vi. Updating the weightings in the adaptive equalizer and go            to procedure “2.”

The pilot codes “ps” is connected to a dedicated input port S4, the4^(th) input slice, of the WF mux 712 in FIG. 7A. It is forillustrations only. The number of inputs may be different than 4, may bemore.

In addition, pilot codes may not need dedicated ports for diagnostic. Inother embodiments, the pilot codes “ps” use a portion of 4^(th) inputport S4, the 4^(th) input slice, of the WF mux 712 in FIG. 7A throughTDM, CDM, and/or FDM techniques. The WF demux 742 in the receive chain724 must accommodate the time, code, and/or frequency demuxing functionsin recovering received pilot codes accordingly.

In another embodiment with time frame by time frame operations,diagnostic signals may feature N independent pilot codes concurrentlyfor the N inputs of the WF mux 712 for a short time slot periodically asa diagnostic time slot, where 4≧N≧1. Majority of the time slots in aframe are dedicated for data transmission only. The WF demux 742 in thereceive chain 724 must accommodate the time demuxing functions for the Nchannels in recovering N independent pilot codes accordingly. Theassociated optimization may use cross correlations as cost functionsamong the N- outputs from the WF demux 742 during the diagnostic timeslots.

FIG. 7B depicts a more detailed flow diagram for a return linktransmissions with WF muxing 764 in an advanced user terminal 633 and acorresponding WF demuxing 742 in the WF mux/demux processing facility714 collocated with a GBBF 412 ground facility.

For a user in a transmission mode, there are 3 functional blocks in theadvanced terminal 633;

-   -   1. A WF mux processing featuring a 4-to-4 WF demuxer 764 to        transform a stream of modulated signal, S1, in slice-1        originated from a transmitter 765, along with a diagnostic        stream in slice-4. Slice-2 and slice-3 are unconnected or        grounded.        -   a. Other nearby users may use slice-2 and/or slice-3 of            other identical WF muxers on individual user terminals for            delivering various data streams, S2 and S3, to the same            ground hub via the same 4 UAVs 620-1 a, 620-1 b, 620-1 d,            and 620-1 d over the same frequent slots f1.,        -   b. Each user signal stream is riding on a unique WF vector.            They would be mutually orthogonal to one other at the            outputs of the WF muxers, if they were generated by a WF            muxer. But they are generated by three identical WF muxers.            In three different user terminals similar to 633.    -   2. The 4 parallel outputs y1, y2, y3, and y4 from the WF muxer        764 are sent to a multibeam beam forming network (BFN) 723 which        forms multiple tracking beams following the dynamics of the        relaying UAVs 620-1. The signal stream y1 is from the output        port wfc-1, y2 from the output port wfc-2, y3 from the output        port wfc-3, and y4 from the output port wfc-4wfc.    -   3. The outputs of the multi-beam transmit BFN 763 are        conditioned, frequency up-converted and power amplified by a        bank of frequency up-converters and power amplifiers 762, before        radiated by array elements 722. The 4 Tx beam signals are mainly        the corresponding signals of y1 targeted for the UAV 620-1 a, y2        targeted for the UAV 620-1 b, y3 targeted for the UAV 620-1 c,        and y4 targeted for the UAV 620-1 d.

Up linked L/S band signals in the foreground are captured and amplifiedby M receiving (Rx) array elements. The M received element signals oneach of the four UAVs 620-1 are transponded and FDM muxed individually.The FDM muxed element signals are relayed back to the GBBF; Thoseelement signals from the UAV M1 a 620-1 a are via a first down link 450a of the Ku/Ka feeder-links 450. Those element signals from the UAV M1 b620-1 b are via a second down link 450 b of the Ku/Ka feeder-links 450.Those element signals from the UAV M1 c 620-1 c and the UAV M1 d 620-1de are, respectively via a third down link 450 c and a 4^(th) downlink450 d of the Ku/Ka feeder-links 450.

These down linked element signals captured by four directional antennas411 in the mobile hub 710, are conditioned by RF frontend units 783,frequency down converted and FDM demuxed to M outputs at a basebandfrequency by FDM demuxers 782, before being sent to multibeam Rx DBFs781. One of the output ports of each of the 4 Rx DBF shall be assignedto the Tx beams with a common beam position 1302 where the user terminal633 is located. The outputs from the beams of the 4 Rx DBF 781 aiming atthe beam position 1302 are designated as y1″, y2″, y3″, and y4″. Theyare the 4 inputs to the receiving processing of the WF muxing/demuxingprocessing facility 714. The receiving processing comprises mainly theequalization functions by a bank of 4 adaptive FIR filters 741, and a WFdemuxing transformation by a 4-to-4 WF demuxer 742.

After fully optimized via iterative equalizations, the optimized outputsfrom the first output port slice-1 will be the recovered signals S1originated from the user terminal 633 in the foreground beam position1302. The recovered S1 has been riding on the WF1. Similarly, theoptimized outputs from the second output port slice-2 will be therecovered signals S2 originated from the second user terminal similar toterminal 633 in the foreground beam position 1302. The recovered S2 hasbeen riding on the WF2.

A receiving processing in the WF muxing/demuxing unit 714 consists of abank of adaptive equalizers 741 and a 4-to-4 WF demuxer 742 toreconstitute the 3 slices of signal streams and a stream of pilot codes;

-   -   (1) The inputs y1′, y2′, y3′, and y4′ are connected to 4        adaptive finite-impulse-response (FIR) filters for time, phase,        and amplitude equalizations among the 4 propagation paths;    -   (2) Individual adaptive filters compensate for phase        differentials caused by “dispersions” among the propagation        paths (array elements) in feeder links via a UAV. There will be        significant improvement on waveform shape distortions due to        dispersions; minimizing a source for inter-symbol interferences.    -   (3) Differences among 4 FIR filters 741 are optimized as a group        to compensate for time and phase differentials among propagating        paths via 4 different UAVs 620-1    -   (4) weightings of the FIR filters 741 are optimized by an        iterative control loop based on comparisons 744 of recovered        pilot signals S4 against the injected and known diagnostic        signals ps and an efficient optimization algorithm in an        optimization processing 743.    -   (5) the filtered outputs from the adaptive FIR filters 741 are        connected to the 4 wfc input ports of the WF demuxer 742.    -   (6) Among the outputs of the WF demuxer 742 are the 3 slices of        desired signal streams, and a pilot signal.        -   a. The WF muxer for the first user is customized to receive            signals from the first slice, or the 1^(st) output port.        -   b. Similarly, the WF muxer for the second user and the third            user are, respectively, customized to receive signals from            the second slice (the 2^(nd) output port) or signals from            the third slice (the 3^(rd) output port).    -   (7) The optimization loop utilizing cost minimization criteria        in the optimization processing 743 comprises:        -   a. Identifying proper observables for the optimization loop            including:            -   differences between the recovered pilot signal stream                and the original.            -   Correlations of signals from output slices of the WF                demuxer 742        -   b. Generating different cost functions based on various            observables            -   Converting or mapping various observables into different                measurables or cost functions which must be positively                defined.                -   a. When an observable meets the desired performance,                    the corresponding measurable or cost function                    becomes zero.                -   b. When an observable is only slightly away from the                    desired performance, the corresponding measurable or                    cost function is assigned with a small positive                    number.                -   c. When an observable is far away from the desired                    performance, the corresponding measurable or cost                    function is assigned with a large positive number.        -   c. Summing all cost function for a total cost as a numerical            indicator the current status of the optimization loop            performances,            -   When total cost is less than a small positive threshold                value, stop the optimization loop;            -   otherwise proceed to procedure d        -   d. Deriving the gradients of total cost with respect to the            weights of the adaptive equalizers which are in the forms of            FIR filters.        -   e. Calculating new weights of the FIR filters based on a            steepest descent algorithm to minimize the total cost of the            optimization loop iteratively.        -   f. Updating the weightings in the adaptive equalizer and go            to procedure b.

Next example presents architectures and methods of implementing forwardlink of mobile communications in a disaster area via largely spacedmultiple small UAVs featuring GBBF or RBFN, and WF muxing/demuxing forcoherent power combining in receivers

We shall use the term “M1 UAVs 620-1” to represent all 4 small UAVs; theM1 a UAV 620-1 a, the M1 b UAV 620-1 b, the M1 c UAV 620-1c, and the M1d UAV 620-1 d in FIG. 7.

FIG. 7 depicts an embodiment via multiple M1 UAVs 620-1 forcommunications mainly to rescue worker community in a coverage area 130.

The ground facility 710 features:

-   -   1. multiple beam antennas 411 to connected to various UAV        platforms 620-1 concurrently via different Ku/Ka band        feeder-links 450,        -   a. link 450 a between the ground facility 710 and M1 a UAV            620-1 a;        -   b. link 450 b between the ground facility 710 and M1 b UAV            620-1 b;        -   c. link 450 c between the ground facility 710 and M1 c UAV            620-1 c;        -   d. link 450 d between the ground facility 710 and M1 d UAV            620-1 d;    -   2. GBBF for both forward link (transmitting) beams and return        link (receiving) beams;    -   3. mobile hubs 413 as gateways to terrestrial networks 480 or        other UAV based networks.

The M1 a, M1 b, M1 c, and M1 d UAVs 620-1 along with their GBBFprocessing feature multiple beams 1301, 1302, 1303, and others in bothforward and return links in a reserved public safety frequency band; eg.4.9 GHz or 700 MHz in US.

The users (rescue worker community) in the coverage areas shall featuremultiple tracking-beam terminals 633. Each of the advanced userterminals exhibits capability of tracking the 4 M1 UAVs 620-1 with fourseparated beams operating at the same frequency slots in a reservedpublic safety band concurrently. For a user 633 with a multi-beamterminal there are 4 concurrent links;

1. link 420 a between the multi-beam user 633 and M1 a UAV 620-1 a;

2. link 420 b between the multi-beam user 633 and M1 b UAV 620-1 b;

3. link 420 c between the multi-beam user 633 and M1 c UAV 620-1 c; and

4. link 420 d between the multi-beam user 633 and M1 d UAV 620-1 d;

Good isolations among multiple UAVs 620-1 operating at same frequencybandwidths, codes and time slots are achieved via spatial isolationsfrom the advanced user terminals. As a result, same spectrum is used 4times more than the scenarios presented in FIG. 5.

WF muxing/demuxing 712/742 is utilized for calibrations andcompensations on unbalanced delays and attenuations among fourpropagation paths and associated electronics. The four paths are:

-   -   1. 450-1 a+620-1 a;    -   2. 450-1 b+620-1 b;    -   3. 450-1 c+620-1 c; and    -   4. 450-1 d+620-1 d;

In forward links of mobile communications via multiple largely space M1UAVs 620-1 with ground based beam forming (GBBF) 412 or remote beamforming network (RBFN) via beam-forming 751 among distributed subarrays;each of which is on a separated UAV. Ku/Ka channels in the feeder links450 shall be designed with adequate instantaneous bandwidths to supportall 4 M1 UAVs 620-1 concurrently. These techniques may include advancemulti-beam antennas for the feeder-links in ground facility providingorthogonal beams connecting to all UAV concurrently facilitatingfrequency reuse. The spacing among the M1 UAVs 520-1 shall vary slowly.As a result, the relative geometries among elements in this distributedand slow-varying array are very important in maintaining coherency amongsubarrays. The slow varying array geometries must be continuouslycalibrated and then properly compensated for forward links.

This operation scenario will allow coherently added stronger radiatedsignals from multiple M1 UAVs 520-1 to “punch through” debris orman-made structures reaching users with disadvantage terminals or atdisadvantaged locations.

It is the WF muxing/demuxing with adaptive equalization process whichdynamically compensates for the differentials of amplitudes and phasesamong the 4 separated propagation paths via 4 individual UAVs based on“recovered” probing signals on WF demuxer, enabling the capability ofcontinuously maintaining “coherency” among signals passing through fourindependent UAVs.

Next example presents architectures and methods of implementing returnlink of mobile communications in a disaster area via largely spacedmultiple small UAVs featuring GBBF or RBFN, and WF muxing/demuxing forcoherent power combining in receivers

For a user in a transmission mode, there are 3 functional blocks in theadvanced terminal 633 as depicted in FIG. 7B;

-   -   1. A WF mux processing featuring a 4-to-4 WF demuxer 764 to        transform a stream of modulated signal, S1, in slice-1        originated from a transmitter 765, along with a diagnostic        stream in slice-4. Slice-2 and slice-3 are unconnected or        grounded.    -   2. The 4 parallel outputs y1, y2, y3, and y4 from the WF muxer        764 are sent to a multibeam beam forming network (BFN) 763 which        forms multiple tracking beams following the dynamics of the        relaying UAVs 620-1. The signal stream y1 is from the output        port wfc-1, y2 from the output port wfc-2, y3 from the output        port wfc-3, and y4 from the output port wfc-4wfc.    -   3. The outputs of the multi-beam transmit BFN 763 are        conditioned, frequency up-converted and power amplified by a        bank of frequency up-converters and power amplifiers 762, before        radiated by array elements 722. The 4 Tx beam signals are mainly        the corresponding signals of y1 targeted for the UAV 620-1 a, y2        targeted for the UAV 620-1 b, y3 targeted for the UAV 620-1 c,        and y4 targeted for the UAV 620-1 d.

Up linked L/S band signals in the foreground are captured and amplifiedby M receiving (Rx) array elements on the UAVs 620-1. The M receivedelement signals on each of the four M1 UAVs 620-1 are conditioned,transponded and FDM muxed individually. The FDM muxed element signalsare relayed back to the GBBF 412. Those element signals from the UAV M1a 620-1 a are via a first down link 450 a of the Ku/Ka feeder-links 450.Those element signals from the UAV M1 b 620-1 b are via a second downlink 450 b of the Ku/Ka feeder-links 450. Those element signals from theUAV M1 c 620-1 c and the UAV M1 d 620-1 d are, respectively via a thirddown link 450 c and a 4^(th) downlink 450 d of the Ku/Ka feeder-links450.

These down linked element signals captured by four directional antennas411 in the mobile hub 710, are conditioned by RF frontend units 783,frequency down converted and FDM demuxed to M outputs at a basebandfrequency by FDM demuxers 782, before being sent to multibeam Rx DBFs781. One of the output ports of each of the 4 Rx DBF shall be assignedto the Tx beams with a common beam position 1302 where the user terminal633 is located. The outputs from the beams of the 4 Rx DBF 781 aiming atthe beam position 1302 are designated as y1″, y2″, y3″, and y4″. Theyare the 4 inputs to the receiving processing of the WF muxing/demuxingprocessing facility 714. The receiving processing comprises mainly theequalization functions by a bank of 4 adaptive FIR filters 741, and a WFdemuxing transformation by a 4-to-4 WF demuxer 742.

After fully optimized via iterative equalizations, the optimized outputsfrom the first output port slice-1 will be the recovered signals S1originated from the user terminal 633 in the foreground beam position1302. The recovered S1 has been riding on the WF1. Similarly, theoptimized outputs from the second output port slice-2 will be therecovered signals S2 originated from the second user terminal similar toterminal 633 in the foreground beam position 1302. The recovered S2 hasbeen riding on the WF2.

The pilot codes “ps” is connected to a dedicated input port S4, the4^(th) input slice, of the WF mux 764 in FIG. 7B. It is forillustrations only. The number of inputs may be different than 4, andpilot codes may not need dedicated ports for diagnostic.

In other embodiments, the pilot codes “ps” using a portion of 4^(th)input port or input slice through TDM, CDM, and/or FDM techniques. TheWF demux 742 in the receive chain 714 must accommodate the time, code,and/or frequency demuxing functions in recovering received pilot codesaccordingly.

In another embodiment with time frame by time frame operations,diagnostic signals may feature N independent pilot codes concurrentlyfor the N inputs of the WF mux 764 for a short time slot periodically asa diagnostic time slot, where 4≧N≧1. Majority of the time slots in aframe are dedicated for data transmission only. The WF demux 742 in thereceive chain 714 must accommodate the time demuxing functions for the Nchannels in recovering N independent pilot codes accordingly. Theassociated optimization may use cross correlations as cost functionsamong the N- outputs from the WF demux 742 during the diagnostic timeslots.

Embodiment 1

This embodiment presents architectures and methods of implementingmobile communications in a disaster area via largely spaced multipleUAVs featuring GBBF or RBFN, and WF muxing/demuxing for transmissionredundancy and data security, not for coherent power combining inreceivers. It uses WF muxing transformation on signals, not onwaveforms, as preprocessing enabling multi-channel propagations ofvarious waveforms on sums of the same multiple signals with differentsets of weighting coefficient. The modulators are placed after WF muxingin the transmission site.

On a multi-channel receiver, received WFM waveforms are demodulated,converting them to WFM signals, which are used to reconstruct originalsignals via a non-coherent combining performed by a corresponding WFdemuxing transformation.

Similar configurations taking advantages of WF muxing/demuxing fornon-coherent combining are applicable to communications via multiplesatellites, air platforms including UAVs, terrestrial mobilecommunications, Passive Optical Network (PON) via optical fibers, and/orInternet IP connectivity for transmission redundancy and better datasecurity. The dynamic transmission features built-in redundancy and dataprivacy. It is always important. For video streaming via multiple mirrorsites in IP Internet network, this is a very powerful tool to gain speedon delivery of video packages.

FIG. 8a and FIG. 8b depict functional flow diagrams for a forward linkand return link transmissions, respectively, with WF muxing/demuxingtechniques not for “coherent power combining” but for data transmissionsecurity and redundancy. The techniques concurrently provide redundancyand camouflage on segment data streams. The transmitted data streams inthe forms of WF muxed segments can be designed, as an example, with a4-for-3 redundancy to enable capability at destinations of recoveringoriginal data streams with any 3 of the 4 WF muxed segments. Each WFmuxed segment is delivered independently via one of the 4 UAVs 620-1.

In the forward link depicted in FIG. 8A from a ground hub 710 to a user633 through 4 UAVs 620-1, WF muxing are utilized to transform 3segmented data streams X1, X2, and X3 from a first user input, X, by a4-to-4 WF muxer 814 into 4 WF domain signals; y1, y2, y3, and y4. Thesegmented streams are generated by a TDM demuxer 812. The input X of theTDM demuxer 812 is flowing at N samples per second, and its threesegmented outputs X1, X2, and X3 are flowing at N/3 samples per second.X1 connected to slice 1 is designated to be sent to the user terminal633 in the beam position 1302. Two other signals connected to slice 2and slice 3 respectively, X2 and X3, are transmitted through the same 4UAVs via WF muxing processing.

A WF muxing device may be implemented in many ways including a FFT, aHadamard matrix in digital formats, or combinations of FFT and Hadamardmatrixes. It may also be constructed by a Butler Matrix (BM) in analoguepassive circuitry. In FIG. 8a , the 4-to-4 WF muxer 814 features a4-to-4 Hadamard matrix. 3 segmented user signals(X1, X2, and X3) areconnected to the first 3 input slices, and a “zero” signals stream(grounding) is connected to the 4^(th) input slice;

The outputs of the WF muxer 814 are various summations of 4 weightedinputs; X1, X2, X3, and “zero signals”. Specifically, y1, y2, y3, and y4are respectively formulated as:

y1(t)=w11*x1(t)+w12*x2(t)+w13*x3(t)+w14*0   (3.1)

y2(t)=w21*x1(t)+w22*x2(t)+w23*x3(t)+w24*0   (3.2)

y3(t)=w31*x1(t)+w32*x2(t)+w33*x3(t)+w34*0   (3.3)

y4(t)=w41*x1(t)+w42*x2(t)+w43*x3(t)+w44*0   (3.4)

where,

-   -   x1(t)=X1, x2(t)=X2, and x3(t)=X3,

and elements in the 4-to-4 Hadamard matrix are arranged in 4 rowvectors:

[w11, w12, w13, w14]=[1, 1, 1, 1]  (3.5)

[w21, w22, w23, w24]=[1, −1, 1, −1]  (3.6)

[w31, w32, w33, w34]=[1, 1, −1, −1]  (3.7)

[w41, w42, w43, w44]=[1, −1, −1, 1]  (3.8)

A wavefront vector (WFV) featuring 4 WF components (wfc) is defined as acolumn matrix of the 4-to-4 Hadamard matrix. There are four such vectors(column matrixes) which are mutually orthogonal:

WFV1=WF1=Transport of [1, 1, 1, 1]  (4.1)

WFV2=WF2=Transport of [1, −1, 1, −1]  (4.2)

WFV3=WF3=Transport of [1, 1, −1, −1]  (4.3)

WFV4=WF4=Transport of [1, −1, −1, 1]  (4.4)

WFX*WFY=1 if X=Y, otherwise WFX*WFY=0; where X and Y are integers from 1to 4.

x1(t), x2(t), x3(t), and “zero signals are, respectively, “attached” toone of the 4 WF vectors by connecting to a corresponding input port ofthe WF muxing device 814.

The outputs y1(t), y2(t), y3(t), and y4(t) are linear combinations ofwavefront components (wfcs); the aggregated data streams. The signalstream y1 is the output from the output port wfc-1, y2 from wfc-2, andso on.

The X1 signal is replicated and appears in all 4 wfc output ports.Actually, X1 is “riding on the WF vector WF1. So are the X2, X3, and“zero” signals.

The 4 outputs, y1, y2, y3, and y4 are connected to 4 separatedmodulators 816 converting data inputs into transmission waveforms. Thereare 4 sets of WFM waveforms at the outputs of the four modulators 816representing 4 segmented data streams; y1, y2, y3, and y4, in the WFmuxed format. The data streams; y1, y2, y3, and y4, are referred as WFMsignals or WFM data; and the corresponding 4 streams of waveforms arethe 4 WFM waveform streams or WFM waveforms.

The 4 sets of waveforms are delivered to 4 separated transmit (Tx)digital beam forming (DBF) processors 751, converting them as parts of 4sets of element signals for arrays on various UAVs. Assuming Ne arrayelements for the L/S band foreground communications on each UAV 620-1, aTx DBF processor 751 shall features Ne element outputs.

Each of the four FDM muxers 752 performs multiplexing on Necorresponding element signals into a single signal stream, which isfrequency up converted and power amplified by a set of RF front end 753before up-loaded by one of the 4 separated high gain antennas 411 to adesignated UAVs 620-1. GBBF 412 features 4 sets of multibeam DBFprocessors 751; each is designated to “service” Ne elements of the arrayfor foreground communications in L/S band.

The 4 separated arrays on 4 UAVs for foreground communications willconcurrently form L/S band beams pointed to the same beam position 1302.As a result, waveforms representing y1 is delivered to the user terminal633 via the first UAV 620-1 a, those for y2 via the second UAV 620-1 b,those for y3 by the third UAV 620-1 c, and those for y4 through the4^(th) UAV 620-1 d.

From the point of view of the X1 signal stream, the X1 signal stream isrelayed to the designated user terminal 633 concurrently by 4 separatedUAVs 620-1 through a common frequency slot f1. From the point of view ofthe X2, and X3 signal stream, they are relayed to the same designateduser terminal 633 concurrently by the 4 separated UAVs 620-1 through acommon frequency slot f1.

At a destination, there are 3 functional blocks in the advanced terminal633; (1) a multibeam antenna, (2) advance WF demuxing processor, and (3)a de-segmenting processing.

Multi-Beam Receiver

Signals transponded by the four UAVs 620-1 are captured, amplified anddemodulated by a multibeam receiving (Rx) array841. The Rx array 841comprises of M array elements 721, each followed by a LNA and frequencydown converter 722 for conditioning received signals. The M parallelconditioned received signals are sent to a multibeam beam formingnetwork (BFN) 723 which forms multiple tracking beams following thedynamics of the 4 relaying UAVs 620-1. The outputs of the multi-beam BFN723 featuring 4 received waveform sets representing data streams, y1′,y2′, y3′, and y4′ are sent to the 4 demodulators 824 for recovery of thedata streams, y1′, y2′, y3′, and y4′ contaminated by additional noisesand external interferences. The qualities (SNR, and/or BER) of therecovered data streams are highly dependent on the communications linksbetween the mobile hub 710 and user terminals via four UAVs.

Advanced WF Demux

A WF demux processing 824 features a processing based on the 4-to-4Hadamard matrix with the 16 parameters depicted in equation (3) WFdemuxer 842 to reconstitute the 3 slices of signal streams X1, X2, andX3 and a stream of zero signals. Based on equation (3), the demodulatedsegment streams (WF muxed segments) via the 4-to-4 Hadamard transform814 shall feature the following;

y1′(t)=x1′(t)+x2′(t)+x3′(t)+0   (5.1)

y2′(t)=x1′(t)−x2′(t)+x3′(t)−0   (5.2)

y3′(t)=x1′(t)+x2′(t)−x3′(t)−0   (5.3)

y4′(t)=x1′(t)−x2′(t)−x3′(t)+0   (5.4)

There are three unknown X1′, X2′, X3′ with 4 linear combinationequations of known values. There is built-in redundancy; only 3 out ofthe 4 demodulated WF muxed segments are needed to reconstruct the 3original segments; X1′, X2′, and X3′.

To take advantage of redundancy in WF muxing processing 814, theadvanced WF demuxing process 842 may not use conventional HadamardMatrix. As an example for illustration, let us assume the 3^(rd) UAVbecomes unavailable. Therefore y3′(t) is absent in the reconstructionprocess. Based on equations (5.1) and (5.4)

y1′(t)+y4′(t)=2*x1′(t)   (5.5a),

therefore,

x1′(t)=½(y1′(t)+y4′(t))   (5.5b)

Based on equations (5.1) and (5.2),

y1′(t)−y2′(t)=2*x2′(t)   (5.6a),

therefore,

x2′(t)=½(y1′(t)−y2′(t))   (5.6b)

Based on equations (5.2) and (5.4),

y2′(t)−y4′(t)=2*x3′(t)   (5.7a)

therefore.

x3′(t)=½(y2′(t)−y4′(t))   (5.7b)

This ad hoc solution is good for 1 of possible 24 possibilities with4-for-3 redundancy.

When all 4 demodulated WF muxed segments from the demodulators 824 areavailable in a 4-for 3 redundancy configuration, there are 5 differentformulations for WF demuxing to reconstruct the 3 segmented data streamsX1, X2, and X3. By comparing 5 results from all possible data reductionformulations, similar techniques using advanced WF demux 842 can be usedto assessing 4 independent propagation paths, determine if the 4 UAVs620-1 relaying “contaminated” data, and even determine which one iscontaminated if only one of the 4 UAVs is compromised.

De-Segmenting Processing

A TDM muxer 843 is used to “de-segment” the three recovered segmenteddata streams X1′, X2′, and X3′. The re-constructed data stream X′ shallflow at the data rate of N samples per second.

In this illustration for forward links, a WF mux processing 814 featuresa processing for creating data security, and redundancy based onsegmented data from a signal data streams. The secured segmented datastreams are delivered to a destination with multibeam receivingcapability. The receiving terminal concurrently captures multiplesegments from 4 UAV platforms. It only requires any three out of the 4segment to faithfully reconstruct the original data streams.

Conceivably, the 3 segmented streams can be three independent datastreams for three targeted users within a common beam position (e.g.1302 in FIG. 7). However, every user must have capability to recover 3out of the 4 WF muxed data streams, and their receiver must becustomized to only access of designated data only. As indicated inequation (5. 5b), (5.6b), and (5.7b), a user may derive the designateddata streams for him or her by manipulating two of three received datastreams.

FIG. 8B depicts a flow diagram for a return link transmissions with WFmuxing 764 in an advanced user terminal 633 and a corresponding WFdemuxing 724 collocated with a GBBF 412 ground facility.

For a user in a transmission mode, there are 3 functional blocks in hisor her advanced terminal 633. A WF mux processing featuring a 4-to-4 WFdemuxer 864 to transform 3 segmented data streams, X1 X2 and X3 in itsfirst input ports (slice-1, slice-2 and slice-3) and zero signal streamin slice-4. X1, X2, and X3 are flowing at a rate of N/3 samples persecond, and are originated from a data stream 725 via a TDM demuxer 862.The input data stream X is flowing at a rate of N samples per second. A4-to-4 Hadamard matrix is used as the functions for the WF muxing 864.Formulations of Hadamard Matrix are depicted in Equation 3. They arerepeated below

y1(t)=w11*x1(t)+w12*x2(t)+w13*x3(t)+w14*0   (3.1)

y2(t)=w21*x1(t)+w22*x2(t)+w23*x3(t)+w24*0   (3.2)

y3(t)=w31*x1(t)+w32*x2(t)+w33*x3(t)+w34*0   (3.3)

y4(t)=w41*x1(t)+w42*x2(t)+w43*x3(t)+w44*0   (3.4)

where

-   -   x1(t)=X1, x2(t)=X2, and x3(t)=X3.

The signal stream y1 is from the output port wfc-1, y2 from the outputport wfc-2, y3 from the output port wfc-3, and y4 from the output portwfc-4wfc. The 4 parallel outputs y1, y2, y3, and y4 are sent to 4parallel modulators 866 before connected to a Tx multibeam beam formingnetwork (BFN) 763 which forms multiple tracking beams following thedynamics of the relaying UAVs 620-1. The modulators 866 convert 4parallel data streams;(y1, y2, y3, and y4) into 4 sets of flowingwaveforms representing the4 parallel data streams.

The outputs of the multi-beam transmit BFN 763 are conditioned,frequency up-converted and power amplified by a bank of frequencyup-converters and power amplifiers 762, before radiated by arrayelements 722. The 4 Tx beam signals are mainly the correspondingwaveforms representing yl targeted for the UAV 620-1 a, thoserepresenting y2 targeted for the UAV 620-1 b, those representing y3targeted for the UAV 620-1 c, and those representing y4 targeted for theUAV620-1 d.

Up linked L/S band signals in the foreground are captured and amplifiedby M receiving (Rx) array elements of each of the 4 UAV 620-1. The Mreceived element signals on each of the four UAVs 620-1 are transpondedand FDM muxed individually. The FDM muxed element signals are relayedback to the GBBF. Those element signals from the UAV M1 a 620-1 a arevia a first down link 450 a of the Ku/Ka feeder-links 450. Those elementsignals from the UAV M1 b 620-1 b are via a second down link 450 b ofthe Ku/Ka feeder-links 450. Those element signals from the UAV M1 c620-1 c and the UAV M1 d 620-1 de are, respectively via a third downlink 450 c and a 4^(th) downlink 450 d of the Ku/Ka feeder-links 450.

These down linked element signals captured by four directional antennas411 in the mobile hub 710, are conditioned by RF frontend units 783,frequency down converted and FDM demuxed to M outputs at a basebandfrequency by FDM demuxers 782, before being sent to multibeam Rx DBFs781. One of the output ports of each of the 4 Rx DBFs 781 shall beassigned to the Rx beams with a common beam position 1302 where the userterminal 633 is located. The outputs from the beams of the 4 Rx DBFs 781aiming at the beam position 1302 are sent to 4 demodulators 811. Theoutputs from the demodulators 811 are designated as y1″, y2″, y3″, andy4″. They are the 4 inputs to the receiving processing of the WFmuxing/demuxing processing facility 714. The receiving processingcomprises mainly a WF demuxing transformation by an advanced WF demuxer812.

A WF demux processing 812 features a processing based on the 4-to-4Hadamard matrix with the 16 parameters depicted in equation (3) WFdemuxer 842 to reconstitute the 3 slices of signal streams X1′, X2′, andX3′ and a stream of zero signals. Based on equation (3), the demodulatedsegment streams (WF muxed segments) via the 4-to-4 Hadamard transform814 shall feature the following;

y1′(t)=x1′(t)+x2′(t)+x3′(t)+0   (6.1)

y2′(t)=x1′(t)−x2′(t)+x3′(t)−0   (6.2)

y3′(t)=x1′(t)+x2′(t)−x3′(t)−0   (6.3)

y4′(t)=x1′(t)−x2′(t)−x3′(t)+0   (6.4)

There are three unknown X1′, X2′, X3′ with 4 linear combinationequations of known values. There is built-in redundancy; only 3 out ofthe 4 demodulated WF muxed segments are needed to reconstruct the 3original segments; X1′, X2′, and X3′.

To take advantage of redundancy in WF muxing processing 864, theadvanced WF demux process 812 will not use conventional Hadamard Matrix.As an example for illustration, let us assume the 3^(rd) UAV becomesunavailable. Therefore y3′(t) is absent in the reconstruction process.Based on equations (6.1) and (6.4):

y1′(t)+y4′(t)=2*x1′(t)   (6.5a),

therefore, x1′(t)=½(y1′(t)+y4′(t))   (6.5b)

Based on equations (6.1) and (6.2):

y1′(t)−y2′(t)=2*x2′(t)   (6.6a),

therefore, x2′(t)=½(y1′(t)−y2′(t))   (6.6b)

Based on equations (6.2) and (6.4)

y2′(t)−y4′(t)=2*x3′(t) (6.7a)

therefore x3′(t)=½(y2′(t)−y4′(t))   (6.7b)

This ad hoc solution is good for 1 of possible 24 possibilities with4-for-3 redundancy.

When all 4 demodulated WF muxed segments from the demodulators 824 areavailable in a 4-for 3 redundancy configuration, there are 5 differentformulations for WF demuxing to reconstruct the 3 segmented data streamsX1, X2, and X3. By comparing 5 results from all possible data reductionformulations, similar techniques using advanced WF demux 842 can be usedto assessing 4 independent propagation paths, determine if the 4 UAVs620-1 relaying “contaminated” data, and even determine which one iscontaminated if only one of the 4 UAVs is compromised.

A TDM muxer 813 is used to “de-segment” the three recovered segmenteddata streams X1′, X2′, and X3′. The re-constructed data stream X′ shallflow at the data rate of N samples per second.

FIG. 8c depicts a numerical example via three different processing anddelivering methods via 4 separated air platforms, e.g. the 4 UAVs 620.An original data set featuring 12 numerical numbers, [1, 2, 3, 4, 5, 6,7, 8, 9, 10, 11, 12], will be “delivered” from a hub H to three usermobile users 1, 2, and 3 via three different methods, respectively. Letus assume all 3 mobile users with advanced multibeam terminals whichwill track the 4 UAVs 640 continuously and simultaneously.

Three different methods for preprocessing features:

1. Method 1; segmentation only.

2. Method 2; segmentation and WF muxing without redundancy

3. Method 3; segmentation and WF muxing with redundancy.

Method 1: The original data is segmented into 4 subsets each with 3numbers as following; x1(n)=[1, 5, 9], x2(N)=[2, 6, 10], x3(N)=[3, 7,11], and x4(N)=[4, 8, 12]. These four subsets are uploaded to 4 UAVs,and delivered to the designated mobile user 1 with a multibeam terminal1, which will need all 4 segmented data subsets for original datareconstitutions.

Method 2; The original data is segmented into 4 subsets each with 3numbers, and then the 4 subsets are concurrently sent to a 4-to-4 WFmuxing device, generating 4 new WF muxed data subsets withoutredundancy. Each segmented subset features 3 numbers; same results fromMethod 1. The segmented subsets are x1(N)=[1, 5, 9], x2(N)=[2, 6, 10],x3(N)=[3, 7, 11], and x4(N)=[4, 8, 12]. The 4 subsets of WF muxed data,yk(N) with k from 1 to 4 and N from 1 to 3, are generated via a 4-to-4WF muxing represented by the following matrix operation;

y1(N)=x1(N)+x2(N)+x3(N)+x4(N)   (6.8.1)

y2(N)=x1(N)−x2(N)+x3(N)−x4(N)   (6.8.2)

y3(N)=x1(N)−x2(N)+x3(N)−x4(N)   (6.8.3)

y4(N)=x1(N)−x2(N)−x3(N)+x4(N)   (6.8.4)

The WF muxed data subsets, y1(N)=[10, 26, 42], y2(N)=[−2, −2, −2],y3(N)=[−4, −4, −4], and y4(N)=[0, 0, 0] are uploaded to 4 UAVsindividually, and delivered to the designated mobile user 2 with amultibeam terminal 2. The terminal for the mobile user 2 will need all 4WF muxed data subsets to reconstitute the original data.

Method 3; The original data is segmented into 3 subsets each with 4numbers, and then the 3 subsets are concurrently sent to a 4-to-4 WFmuxing device, generating 4 new WF muxed data subsets. As a result,there exists built-in redundancy. Each segmented subset features 4numbers, and they are x1(N)=[1, 4, 7, 10], x2(N)=[2, 5, 8, 11], andx3(N)=[3, 6, 9, 12]. The 4 subsets of WF muxed data, yk(N) with k from 1to 4 and N from 1 to 4, are generated via a 4-to-4 WF muxing representedby the following matrix operation;

y1(N)=x1(N)+x2(N)+x3(N)+0   (6.9.1)

y2(N)=x1(N)−x2(N)+x3(N)−0   (6.9.2)

y3(N)=x1(N)−x2(N)+x3(N)−0   (6.9.3)

y4(N)=x1(N)−x2(N)−x3(N)+0   (6.9.4)

The 4 WF muxed data subsets, y1(N)=[5, 15, 24, 33], y2(N)=[2, 5, 8, 11],y3(N)=[0, 3, 6, 9], and y4(N)=[−4, −7, −10, −13] are uploaded to 4 UAVsindividually, and delivered to the designated mobile user 3 with amultibeam terminal 3. The terminal for the mobile user 3 will only needany three of the 4 WF muxed data subsets to reconstitute the originaldata. There is a feature of building redundancy.

End of Embodiment 1 Embodiment 2

This embodiment presents architectures and methods of implementingcalibrations and compensations among multiple channels in feeder-linksfor GBBF using WF muxing and demuxing. Element signals and knowndiagnostic (probing) signals will be assigned and attached to variousmulti-dimensional WF vectors. Various multi-dimensional WF vectorcomponents will utilize different propagation channels in thefeeder-links.

FIG. 9a features forward link calibrations with an on-board adaptiveequalization/optimization loop before WF demuxing. Parts of the WFdemuxing outputs on a UAV are recovered diagnostic signals which areused by the optimization loop.

FIG. 9b features forward link calibrations with an on-ground adaptiveequalization/optimization loop before WF demuxing. Parts of the WFdemuxing outputs on a UAV are recovered diagnostic signals which areturned around and passed to ground facility to be used by the groundbased optimization loop.

FIG. 9c features return link calibrations with an on-ground adaptiveequalization/optimization loop before WF demuxing. Parts of the WFdemuxing outputs on ground are recovered diagnostic signals which areused by the ground based optimization loop.

FIG. 9d features ground-based processing.

FIGS. 9a, 9b and 9c depict functional flow diagrams for a forward linktransmissions, respectively, with WF muxing/demuxing techniques forchannel equalizations for feeder-links between a ground facility and anUAVs. It is not for “coherent power combining” among multiple UAVs. Itis also not for data transmission security and redundancy.

The techniques will enable communication architecture designer moreflexibility to utilize feederlinks. We will use 32-to-32 FFTtransformations as WF muxing and demuxing functions in the illustration.

Calibrations and compensations of a GBBF processing with a moving UAVplatform continuously shall include (1) phase and amplitude differentialof unbalanced electronics on board an UAV, (2) phase and amplitudedifferential of unbalanced electronics on ground facility, (3) phase andamplitude differential due to Ka/K band propagation effects in afeeder-link.

The illustrations are focused to the dynamic compensation offeeder-links at Ku-band. We assume the total available feeder-linebandwidth in a Ku band for forward link is 500 MHz bandwidth in verticalpolarization (VP), and the same 500 MHz in horizontal polarization (HP).The 500 MHz at VP is divided into 16 contiguous frequency slots eachwith ˜31 MHz bandwidth. Similarly the 500 MHz at HP is also divided intoa second 16 contiguous frequency slots. There total 32 frequency slotsassigned to forward links from a ground facility to an UAV features anup-link spectrum around 14 GHz . These allow an operator to continuouslysupport a Tx array with ≦30 elements on an UAV for GBBF operations withfull calibration continuously. Each element features a bandwidth of ˜30MHz.

Similarly we may assume the total available feeder-line bandwidth in aKu band for return link is also 500 MHz bandwidth in verticalpolarization (VP), and the same 500 MHz in horizontal polarization (HP).The 500 MHz at VP is divided into 16 contiguous frequency slots eachwith ˜31 MHz bandwidth. Similarly the 500 MHz at HP is also divided intoa second 16 contiguous frequency slots. There total 32 frequency slotsassigned to return links from UAVs to a ground features an down-linkspectrum around 12 GHz . These allow an operator to continuously supportan Rx array with ≦30 elements on an UAV for GBBF operations with fullcalibration continuously. Each element features a bandwidth of ˜30 MHz

In the examples of FIGS. 9a, 9b, and 9c we assume each UAV features 10L/S band array elements, each with 30 MHz bandwidth, via GBBF forforeground communications.

It is noticed that one such feeder-link may support 3 UAVs concurrently.It is possible to have multiple feederlinks to a single UAV frommultiple hubs to perform GBBF concurrently using the same 10 L/S bandarray elements

FIG. 9a is functional flow diagram from ground processing facility to aUAV for forward link calibrations of the feeder-link. On a GBBFprocessing facility 910 on ground, multiple “beam” inputs 915 are sentto a multi-beam Tx DBF processor 751 for a remote array with 10 arrayelements 939 on a UAV. The outputs from the Tx DBF are 10 parallelprocessed data streams for the transmissions by the designated elements939. These processed signals are referred to as element signals (Es1, .. . , Es10) which are respectively, connected to the first 10 slices ofa 32-to-32 WF muxer 914. The WF muxer features a 32-to-32 FFT function,and may be implemented as an S/W package in a digital circuit either ina single monolithic chip or a digital circuit board.

Many of the input ports, or slices, are not connected. We “ground” thelast 4-slices, input ports 29 through 32, as inputs to diagnosticsignals with “zero” signals. At the 32 outputs are 32 different linearcombinations of the 10 designated element signals. These output portsare referred to as 12 wavefront component (wfc) ports and the outputsare 12 aggregated data streams. The signal stream y1 is the output fromthe output port wfc-1, y2 from wfc-2, and so on.

As a result of the WF muxing, there are 32 WF vectors which are mutuallyorthogonal among the 32wfc outputs. Each WF vector features 32components distributed among the 32 wfc ports. Every input port (slice)is associated to a unique WF vector. Since Es1 is connected to slice-1,Es1 is “attached” to the first WF vector, or “riding on WF1”.

The first 16 output (wfc) ports are FDM muxed into IF signals with 500MHz bandwidth by a FDM Mux1 752. The muxed signals are then frequencyup-converted and power amplified via a RF frontend unit 933, beforeradiated by a directional antenna 411 in vertical polarization (VP) tothe designated UAV 620-1 a. The amplified signals are radiated via a VPformat by connecting the amplified signals to a first input (VP) port ofan Orthomode-T 912 for the feed of the directional antenna 411.

The second 16 output (wfc) ports are FDM muxed into IF signals with 500MHz bandwidth by a FDM Mux2 752. The muxed signals are then frequencyup-converted and power amplified via a RF front-end unit 933, beforeradiated by a directional antenna 411 in horizontal polarization (HP) tothe designated UAV 620-1 a. The amplified signals are radiated via a HPformat by connecting the amplified signals to a second input (HP) portof an Orthomode-T 912 for the feed of the directional antenna 411.

On board a moving platform, UAV 620-1 a, a “coherent transponding”process is illustrated in the panel 930. A high gain tracking antenna931 picks up the up-loaded signals from a ground processing facility910. The transponding process 930 converts one input at Ku bandreceiving antenna 931 into 10 outputs for 10 elements 939 in L/S bandconcurrently.

The output from the high gain antenna 931 is split into HP and VPsignals through an orthomode-T 932; each goes through an RF front-endunit 933 and a FDM demuxer 934 converting a 500 MHz muxed signal into 16channelized signals. These channelized signals are at a common IF with˜30 MHz bandwidth each. There are total 32 channelized signals which areconnected to the 32 inputs of a 32-to-32 WF demuxer 942 via 32 paralleladaptive equalizers 941

The 16 channelized signals come from the VP port of the Orthomode-T 932are assigned to the first 16 (wfc) ports of the WF demuxer 942, and the16 channelized signals come from the HP port of the “Orthomode-T”932 areto the next 16 (wfc) ports of the WF demuxer 942.

An optimization loop is built among (1) the 32 sets of FIR weighting inthe adaptive equalizer 941, (2) recovered diagnostic signals 944 fromthe 4 designated output ports of the WF demuxer 942; slice-29 throughslice-32, and (3) the optimization processing 943 with selectediterative algorithms. In addition to differences of recovered diagnosticsignals and known original diagnostic signals, correlations between theports of element signals (slice-1 through slice-10) and the ports ofdiagnostic signals (slice-29 through slice-32) are important observablesfor the optimization processing 943.

1. The inputs y1′, y2′, y3′, . . . , and y32′ to the WF demux 942 areconnected to 32 adaptive finite-impulse-response (FIR) filters 941 fortime, phase, and amplitude equalizations among the 32 propagationchannels;

2. Adaptive filters compensate for phase differentials caused by“dispersions” among the propagation paths (array elements) in feederlinks via a UAV 620-1 a. There will be significant improvement onwaveform shape distortions due to dispersions; minimizing a source forinter-symbol interferences.

3. weightings of the FIR filters 941 are optimized by an iterativecontrol loop based on comparisons of recovered pilot signals 944 againstthe injected and known diagnostic signals 916, correlations between theports of element signals (slice-1 through slice-10) and the ports ofdiagnostic signals (slice-29 through slice-32), and an efficientoptimization algorithm in an optimization processing 943.

4. Among the outputs of the WF demuxer 942 are the 10 slices of desiredelement signal streams, and 4 pilot signals.

5. The optimization loop utilizing cost minimization criteria in theoptimization processing 743 comprises:

-   -   a. Identifying proper observables for the optimization loop        including:        -   i. differences between the recovered pilot signal stream and            the original.        -   ii. Correlations of signals from output slices of the WF            demuxer 742.    -   b. Generating different cost functions based on various        observables:        -   i. Converting or mapping various observables into different            measurables or cost functions which must be positively            defined.            -   When an observable meets the desired performance, the                corresponding measurable or cost function becomes zero.            -   When an observable is only slightly away from the                desired performance, the corresponding measurable or                cost function is assigned with a small positive number.            -   When an observable is far away from the desired                performance, the corresponding measurable or cost                function is assigned with a large positive number.    -   c. Summing all cost function for a total cost as a numerical        indicator the current status of the optimization loop        performances,        -   i. When total cost is less than a small positive threshold            value, stop the optimization loop;        -   ii. otherwise proceed to procedure d    -   d. Deriving the gradients of total cost with respect to the        weights of the adaptive equalizers which are in the forms of FIR        filters.    -   e. Calculating new weights of the FIR filters based on a        steepest descent algorithm to minimize the total cost of the        optimization loop iteratively.    -   f Updating the weightings in the adaptive equalizer and go to        procedure b.

At an optimized state, the amplitude and phase responses of the 32frequency channels in the feeder-link shall be fully equalized. Thus the32 associated WF vectors shall become mutually orthogonal at theinterfaces between the 32 outputs of the adaptive equalizers 941 and the32 inputs of the WF demuxer 942. Thus there are no leakages among theoutputs of the WF demuxer 942; cross correlations among signals indiagnostic channels (slice-29 through slice-32) and element signalschannels (slice-01 through slice-10) shall become zero.

As a result, the recovered element signals from slice 1 through slice 10are frequency up converted and filtered via frequency up-converters 937to L/S band, power amplified by PAs 938 before radiated by radiatingelements 939. The 10 radiated signals processed by DBF 751 in the GBBFfacility 910 will be spatial power combined in far field over differentdesignated beam positions in a coverage area 130 for various usersignals.

In this scheme, it is assume that the 10 parallel channels are fullyequalized between the radiating elements 939 and beyond the outputs ofthe WF demuxer 942.

FIG. 9b is nearly identical to FIG. 9a . Both depict functional flowdiagrams from ground processing facility to a UAV for forward linkcalibrations of the feederlink. The only differences are the locationsof the adaptive equalizations and optimization loop. Instead of on-boardadaptive equalization, FIG. 9b features a scheme with ground baseadaptive equalizations and optimization loop for the feeder-links forforward link signals.

On a GBBF processing facility 910 on ground, multiple “beam” inputs 915are sent to a multi-beam Tx DBF processor 751 for a remote array with 10array elements 939 on a UAV 620-1 a. The outputs from the Tx DBF 751 are10 parallel processed data streams for the transmissions by thedesignated elements 939. These processed signals are referred to aselement signals (Es1, . . . , Es10) which are respectively, connected tothe first 10 slices of a 32-to-32 WF muxer 914. The WF muxer features a32-to-32 FFT function, and may be implemented as an S/W package in adigital circuit either in a single monolithic chip or a digital circuitboard.

Many of the input ports, or slices, are not connected. We “ground” thelast 4-slices, input ports 29 through 32, as inputs to diagnosticsignals with “zero” signals. At the 32 outputs of the WF muxer 914 are32 different linear combinations of the 10 designated element signals.These output ports are referred to as 32 wavefront component (wfc) portsand the outputs are 32 aggregated data streams. The signal stream y1 isthe output from the output port wfc-1, y2 from wfc-2, and so on.

As a result of the WF muxing, there are 32 WF vectors which are mutuallyorthogonal among the 32wfc outputs. Each WF vector features 32components distributed among the 32 wfc ports. Every input port (slice)is associated to a unique WF vector. Since Es1 is connected to slice-1,Es1 is “attached” to the first WF vector, or “riding on WF1”.

The first 16 output (wfc) ports are connected to a first set of 16parallel adaptive equalizers 941 and then FDM muxed into IF signals with500 MHz bandwidth by a FDM Mux1 752. The adaptive equalizers 941 are forcompensations via pre-distortions on cumulated amplitudes and phasedifferentials of propagating signals in selected 32 channels in afeederlink 450. The muxed signals are than frequency up-converted andpower amplified via a RF frontend unit 753, before radiated by adirectional antenna 411 in vertical polarization (VP) to the designatedUAV 620-1 a. The amplified signals are radiated via a VP format byconnecting the amplified signals to a first input (VP) port of an“Orthomode-T” 912 for the feed of the directional antenna 411.

The second 16 output (wfc) ports are connected to a second set of 16parallel adaptive equalizers 941 and then FDM muxed into IF signals with500 MHz bandwidth by a FDM Mux2 752. The muxed signals are thanfrequency up-converted and power amplified via a RF front-end unit 753,before radiated by a directional antenna 411 in horizontal polarization(VP) to the designated UAV 620-1 a. The amplified signals are radiatedvia a HP format by connecting the amplified signals to a second input(HP) port of an Orthomode-T 912 for the feed of the directional antenna411.

On board a moving platform, UAV 620-1 a, a “coherent transponding”process is illustrated in the panel 930. A high gain tracking antenna931 picks up the up-loaded signals from a ground processing facility910. The transponding process 930 converts one input at Ku bandreceiving antenna 931 into 10 outputs for 10 elements 939 in L/S bandconcurrently.

The output from the high gain antenna 931 is split into HP and VPsignals through an Orthomode-T 932; each goes through an RF front-endunit 933 and a FDM demuxer 934 converting a 500 MHz muxed signal into 16channelized signals. These channelized signals are at a common IF with˜30 MHz bandwidth each. There are total 32 channelized signals which areconnected to the 32 inputs of a 32-to-32 WF demuxer 942.

The 16 channelized signals come from the VP port of the Orthomode-T 932are assigned to the first 16 (wfc) ports of the WF demuxer 942, and the16 channelized signals come from the HP port of the Orthomode-T 932 areto the next 16 (wfc) ports of the WF demuxer 942.

An optimization loop is built among (1) the 32 sets of ground-based FIRfilter weighting in the adaptive equalizer 941, (2) recovered diagnosticsignals 944 from the 4 designated output ports of the on-board WFdemuxer 942; slice-29 through slice-32, and (3) the optimizationprocessing 943 with selected iterative algorithms on ground. In additionto differences of recovered diagnostic signals and known originaldiagnostic signals, correlations between the ports of element signals(slice-1 through slice-10) and the ports of diagnostic signals (slice-29through slice-32) are important observables for the optimizationprocessing 943.

1. The inputs y1′, y2′, y3′, . . . , and y32′ to the on board WF demux942 can “modulated” by 32 ground based adaptive finite-impulse-response(FIR) filters 941 for time, phase, and amplitude equalizations among the32 propagation channels via compensations via pre-distortionstechniques;

2. Adaptive filters compensate for phase differentials caused by“dispersions” among the propagation paths (array elements) in feederlinks via a UAV 620-1 a. There will be significant improvement onwaveform shape distortions due to dispersions; minimizing a source forinter-symbol interferences.

3. Weightings of the FIR filters 941 are optimized by an iterativecontrol loop based on comparisons of recovered pilot signals 944 againstthe injected and known diagnostic signals 916, and an efficientoptimization algorithm in an optimization processing 943.

4. Among the outputs of the WF demuxer 942 are the 10 slices of desiredelement signal streams, and 4 recovered pilot signals.

5. The recovered pilot signals 944 are piped down to the GBBF facilityvia additional input channels to the on-board WF muxer for calibrationof the Return link (as depicted in FIG. 9c ). As a result, the on-boardrecovered diagnostic signals 944 shall appear on the ground processingfacility 910 as a set of contaminated recovered diagnostic signals 945.

6. The optimization loop utilizing cost minimization criteria in theoptimization processing 943 comprises:

-   -   a. Identifying proper observables for the optimization loop        including:        -   i. differences between the recovered pilot signal stream and            the original.        -   ii. Correlations of signals from output slices of the WF            demuxer 942.    -   b. Generating different cost functions based on various        observables;        -   i. Converting or mapping various observables into different            measurables or cost functions which must be positively            defined.            -   When an observable meets the desired performance, the                corresponding measurable or cost function becomes zero.            -   When an observable is only slightly away from the                desired performance, the corresponding measurable or                cost function is assigned with a small positive number.            -   When an observable is far away from the desired                performance, the corresponding measurable or cost                function is assigned with a large positive number.    -   c. Summing all cost function for a total cost as a numerical        indicator the current status of the optimization loop        performances,        -   i. When total cost is less than a small positive threshold            value, stop the optimization loop;        -   ii. otherwise proceed to procedure d    -   d. Deriving the gradients of total cost with respect to the        weights of the adaptive equalizers which are in the forms of FIR        filters.    -   e. Calculating new weights of the FIR filters based on a        steepest descent algorithm to minimize the total cost of the        optimization loop iteratively.    -   f Updating the weightings in the adaptive equalizer and go to        procedure b.

At an optimized state, the amplitude and phase responses of the 32frequency channels in the feeder-link shall be fully equalized. Thus the32 associated WF vectors shall become mutually orthogonal at theinterfaces between the 32 outputs of the adaptive equalizers 941 and the32 inputs of the WF demuxer 942. Thus there are no leakages among theoutputs of the WF demuxer 942; cross correlations among signals indiagnostic channels (slice-29 through slice-32) and element signalschannels (slice-01 through slice-10) shall become zero.

As a result, the recovered element signals from slice 1 through slice 10are frequency up converted and filtered via frequency up-converters 937to L/S band, power amplified by PAs 938 before radiated by radiatingelements 939. The 10 radiated signals processed by DBF 751 in the GBBFfacility 910 will be spatial power combined in far field over differentdesignated beam positions in a coverage area 130 for various usersignals.

In this scheme, it is assume that the 10 parallel channels are fullyequalized between the radiating elements 939 and beyond the outputs ofthe WF demuxer 942.

FIG. 9c depicts functional flow diagrams from ground processing facilityto a UAV for return link calibrations of the feederlink. It has anadditional feature of supporting the forward link calibrations asdepicted in FIG. 9 b.

On board a mobile platform UAV 620-1 a, a set of 10 array elements 968captures radiated signals in L/S band over a coverage area 130. Thesecaptured element signals are amplified by LNAs 969 and filtered andfrequency converted individually by frequency converter units 967. Theseprocessed signals are referred to as element signals (Es1, . . . , Es10)which are respectively, connected to the first 10 slices of a 32-to-32WF muxer 914. The WF muxer features a 32-to-32 FFT function, and may beimplemented as an S/W package in a digital circuit either in a singlemonolithic chip or a digital circuit board. The WF muxing functions mayalso be implemented as RF Bulter matrixes or a baseband FFT chip.

Many of the input ports, or slices, are not connected. We “ground” thelast 4-slices, input ports 29 through 32, as inputs to diagnosticsignals with “zero” signals. Four input ports 944 from slice-25 throughslice-28 are used for relaying the recovered diagnostic signals from theforward link calibration. They are connected by 4 output ports (theslice-29, slice-30, slice-31, and slice-32) 944 of the WF demuxer 942 inFIG. 9 b.

At the 32 outputs of the WF muxer 914 are 32 different linearcombinations of the 10 designated element signals. These output portsare referred to as 32 wavefront component (wfc) ports and the outputsare 32 aggregated data streams. The signal stream y1 is the output fromthe output port wfc-1, y2 from wfc-2, and so on.

As a result of the WF muxing, there are 32 WF vectors which are mutuallyorthogonal among the 32wfc (output) ports. Each WF vector features 32components distributed among the 32 wfc ports. Every input port (slice)is associated to a unique WF vector. Since Es1 is connected to slice-1,Es1 is “attached” to the first WF vector, or “riding on WF1”.

The first 16 output (wfc) ports are FDM muxed into IF signals with 500MHz bandwidth by a FDM Mux1 964. The muxed signals are than frequencyup-converted and power amplified via a RF frontend unit 963, beforeradiated by a directional antenna 931 in vertical polarization (VP) tothe designated UAV 620-1 a. The amplified signals are radiated via a VPformat by connecting the amplified signals to a first input (VP) port ofan Orthomode-T 962 for the feed of the directional antenna 931.

The second 16 output (wfc) ports are FDM muxed into IF signals with 500MHz bandwidth by a FDM Mux2 964. The muxed signals are than frequencyup-converted and power amplified via a RF front-end unit 963, beforeradiated by a directional antenna 931 in horizontal polarization (HP) toa GBBF processing facility 910. The amplified signals are radiated via aHP format by connecting the amplified signals to a second input (HP)port of an Orthomode-T 962 for the feed of the directional antenna 931.

In the GBBF facility 910, a high gain tracking antenna 931 picks up thedown-loaded signals from an UAV 620-1 a. A transponding process in 910converts one input at Ku band receiving antenna 411 into 10 elementinputs for the RX DBF processor 781

The output from the high gain antenna 411 is split into HP and VPsignals through an Orthomode-T 982; each goes through an RF front-endunit 933 and a FDM demuxer 934 converting a 500 MHz muxed signal into 16channelized signals. These channelized signals are at a common IF with˜30 MHz bandwidth each. There are total 32 channelized signals which areconnected to the 32 inputs of a 32-to-32 WF demuxer 942 through a bankof 32 adaptive equalizers 971 implemented by 32 adaptive FIR filters. .

The 16 channelized signals come from the VP port of the Orthomode-T 932are assigned to the first 16 (wfc) ports of the WF demuxer 942, and the16 channelized signals come from the HP port of the Orthomode-T 932 areto the next 16 (wfc) ports of the WF demuxer 942.

An optimization loop is built among (1) the 32 sets of FIR filterweighting in the adaptive equalizer 971, (2) recovered diagnosticsignals 978 from the 4 designated output ports of the WF demuxer 972;slice-29 through slice-32, and (3) the optimization processing 977 withselected iterative algorithms. In addition to differences of recovereddiagnostic signals and known original diagnostic signals, correlationsbetween the ports of element signals (slice-1 through slice-10) and theports of diagnostic signals (slice-29 through slice-32) are importantobservables for the optimization processing 977.

-   -   1. The inputs y1′, y2′, y3′, . . . , and y32′ to the WF demux        972 can “modulated” by 32 adaptive finite-impulse-response (FIR)        filters 971 for time, phase, and amplitude equalizations among        the 32 propagation channels via compensations via        pre-distortions techniques;    -   2. Adaptive filters compensate for phase differentials caused by        “dispersions” among the propagation paths (array elements) in        feeder links via a UAV 620-1 a. There will be significant        improvement on waveform shape distortions due to dispersions;        minimizing a source for inter-symbol interferences.    -   3. weightings of the FIR filters 971 are optimized by an        iterative control loop based on comparisons of recovered pilot        signals 978 against the injected and known diagnostic signals        974, and an efficient optimization algorithm in a forward link        optimization processing 977.    -   4. Among the outputs of the WF demuxer 972 are the 10 slices of        desired element signal streams, and 4recovered pilot signals 978        for return link (from slice-29 through slice-32).    -   5. “contaminated recovered pilot signals 945 for forward links        are available at the 4 output ports (from slice-25 through        slice-28).    -   6. The optimization loop utilizing cost minimization criteria in        the optimization processing 943 comprises:        -   a. Identifying proper observables for the optimization loop            including            -   i. differences between the recovered pilot signal stream                and the original.            -   ii. Correlations of signals from output slices of the WF                demuxer 942.        -   b. Generating different cost functions based on various            observables            -   i. Converting or mapping various observables into                different measurables or cost functions which must be                positively defined.                -   When an observable meets the desired performance,                    the corresponding measurable or cost function                    becomes zero.                -   When an observable is only slightly away from the                    desired performance, the corresponding measurable or                    cost function is assigned with a small positive                    number.                -   When an observable is far away from the desired                    performance, the corresponding measurable or cost                    function is assigned with a large positive number.        -   c. Summing all cost function for a total cost as a numerical            indicator the current status of the optimization loop            performances,            -   i. When total cost is less than a small positive                threshold value, stop the optimization loop;            -   ii. otherwise proceed to procedure d.        -   d. Deriving the gradients of total cost with respect to the            weights of the adaptive equalizers which are in the forms of            FIR filters.        -   e. Calculating new weights of the FIR filters based on a            steepest descent algorithm to minimize the total cost of the            optimization loop iteratively.        -   f Updating the weightings in the adaptive equalizer and go            to procedure b.

At an optimized state, the amplitude and phase responses of the 32frequency channels in the feeder-link shall be fully equalized. Thus the32 associated WF vectors shall become mutually orthogonal at theinterfaces between the 32 outputs of the adaptive equalizers 971 and the32 inputs of the WF demuxer 972. Thus there are no leakages among theoutputs of the WF demuxer 972; cross correlations among signals indiagnostic channels (slice-29 through slice-32) and element signalschannels (slice-01 through slice-10) shall become zero.

As a result, the recovered element signals from slice 1 through slice 10are sent to a Rx DBF 785 in the GBBF processing facility 911

End of Embodiment 2 Embodiment 3

This embodiment presents architectures and methods of implementingmultiplexing of three users utilizing 4 UAV based communicationschannels through Wavefront multiplexing/de-multiplexing. Each of thethree user signals after WF muxing features a unique wavefront (WF)through a WF vector which propagates through multiple UAV channelsconcurrently. There are three users associated with three mutuallyorthogonal WF vectors. The remaining fourth vector is assigned fordiagnostic signals.

FIG. 10a is for the first user signal stream. The adaptive equalizationloop assures the orthogonality among the four recovered WF vectors. FIG.10b is the block diagram for the second user, and FIG. 10c for the thirduser signals.

FIGS. 10a, 10b, and 10c depict functions of a WF muxing 712 and a WFdemuxing processor 742 concurrently utilizing four independentcommunications assets in four UAVs for three separated users xa, xb, andxc.

Three user forward link signals 1011 a, 1011 b and 1011 c are convertedinto 4 WF components y1, y2, y3, and y4 by a 4-to-4 WF muxer 712 beforeuploaded to 4 separated UAVs 620-1 a, 620-1 b, 620-1 c, and 620-1 d. TheWF muxer is a 4-to-4 Hadamard matrix. As a result, the four outputsignals by 4 wfc ports of the WF muxer;

y1(t)=0+xa(t)+xb(t)+xc(t)   (7.1)

y2(t)=0−xa(t)+xb(t)−xc(t)   (7.2)

y3(t)=0+xa(t)−xb(t)−xc(t)   (7.3)

y4(t)=0−xa(t)−xb(t)+xc(t)   (7.4)

Where the A1 slice is grounded, A2, A3, and A4 slices are connected byxa, xb and xc signals respectively. Every input signal stream goesthrough all 4 UAVs concurrently. The four input signals including the“zero” signal inputs to input slice A1, are riding 4 mutually orthogonalWF vectors at the outputs of the WF muxer 712;

-   -   “zero” signals connected to the A1 slice are associated with        WFV1=[1,1,1,1]^(T),    -   xa(t) signals connected to the A2 slice are associated with        WFV2=[1, −1,1, −1]^(T),    -   xb(t) signals connected to the A3 slice are associated with        WFV3=[1,1, −1, −1]^(T), and    -   xc(t) signals connected to the A4 slice are associated with        WFV4=[1, −1,1, −1]^(T) .

The four parallel paths on a receiver will feature different amplitudeattenuations/amplifications and phase delays even at same carrierfrequency due to path length differentials and unbalanced electronicsamong the four UAV platforms.

The 4 inputs to a bank of 4 parallel adaptive equalizers 741 on a userterminal for the first user feature:

z1(t)=am1a* exp(j kΔz1a)*y1(t),   (8-1)

z2(t)=am2a* exp(j kΔz2a)*y2(t),   (8-2)

z3(t)=am3a* exp(j kΔz3a)*y3(t),   (8-3)

z4(t)=am4a* exp(j kΔz4a)*y4(t),   (8-4)

The adaptive equalizers are to compensate the amplitude and phasedifferentials among the four propagation paths. Their outputs areconnected to the inputs to a 4-to-t WF demuxer 742. The four WF vectorsshall be distorted and no longer mutually orthogonal to one another, Asa results, there are leakages at the output port (slice) A1 from signalsdesignated for A2, A3, and A4 ports. The diagnostic port no longerfeatures “zero” signals.

An optimization loop will use the leakage power 744 as one of theobservables. An optimization processor will convert the observables intoa quantitative measurables, or cost functions, which are alwayspositively defined. Total cost, the sum of all cost functions, andgradients of the total cost are derived and measured. New weights arecalculated and updated based on a steepest descent method for theadaptive equalizers iteratively via a cost minimization algorithm.

In optimized states, four propagation paths shall be fully compensatedso that the inserted phases and amplitudes of the adaptive equalizers[a1*exp(j Φ1)], [a2*exp(jΦ2)], [a3*exp(jΦ3)], and [a4*exp(jΦ4)], mustfulfill the following requirements, respectively:

am1a*exp(j kΦz1a)*[a1*exp(j Φ1)]

=am2a*exp(j kΦ2a)*[a2*exp(j Φ2)]

=am3a*exp(j kΦ3a)*[a3*exp(j Φ3)]

=am4a*exp(j kΦ4a)*[a4*exp(j Φ4)]=constant   (⁹)

As a result, the associated WF vectors after the adaptive equalizerswill become orthogonal again. There are no more leakages at output port(slice) Al of the WF demuxer 742 from the other three output ports(slices A2, A3, and A4).

The signal stream xa recovered on slice A2 1041a is connected to thedesignated receiver for the first user.

FIG. 10b , and FIG. 10c depict the same uplinks but a different downlinks for a second user and a third user at the same beam positions asthat of the first user. The signals output for the second user xb isfrom slice A3 of the WF demuxer 742. The signals output for the thirduser xc is from slice A4 of the WF demuxer 742.

End of Embodiment 3. Embodiment 4

This embodiment presents architectures and methods of implementing UAVbased communications using retro-directive antennas, and ground basedbeam forming (GBBF). Several scenarios are presented as followed;

-   -   1. Analogue retro-directive antennas for on-board feeder-link        payloads in FIG. 11,    -   2. With GBBF but without retro-directive in FIG. 12,    -   3. With GBBF and with retro-directive in FIG. 12 a,    -   4. Without GBBF but with retro-directive in FIG. 12 b.

FIG. 11 depicts of a Ku retro-directive array on board a UAV. Ku-bandarrays 1100 are used for UAVs as feeder link antennas to transfer allsignals to and from L/S or C-band elements channels to a gateway where asimple GBBF processing will perform both Tx and Rx array functions. TheKu band “smart” arrays will feature retro-directivity via on-boardanalogue beam forming network (BFN) 1121 and beam controller 1140technologies.

The 4 element array 1100 features analog beam-forming and switchingmechanisms to gain 6 dB advantage than an omni directional antenna fordata links from a UAV to a ground processing center. The depicted smartarray 1100 featuring four low profile elements 1132 consists of tworegular analogue multiple-beam beam-forming-networks (BFNs) using ButlerMatrixes (BMs); one for Rx 1121 and the other for Tx 1111. However,retro-directive antennasfor the back-channels may be arrays with 8, 16,or more elements depending on how far the UAV is away from the groundprocessing center.

The 4 element array 1100 features 4 Rx beams. Received signals by the 4array elements 1132 after the diplexers 1131 are amplified by LNAs 1123followed by a BPF (not shown) before a receiving (Rx) BM 1121. The Rx BM1121 will form 4 orthogonal beams pointing to 4 separated directionscovering the entire field of view (FOV) of interest. The beam-width ofany one beam will be ½ of the FOV (1/4 in terms of stereo-angles), andthe four orthogonal beams will cover the entire FOV. Furthermore thepeak of any one beam is always a null of all three other beams. Theground processing center will always be covered by one of the fourbeams. When the 4 elements are on a squared lattice with λ/2 in betweenadjacent elements and assuming λ/2 squared element size for all 4elements, the 3-dB beam widths from the 4 element array will be ˜60°near bore side.

The Rx BM 1121 has 4 outputs; each associated with one of the 4 beampositions. There are two parallel switching trees (ST) 1122 connected tothe RX BM in Rx, one for the main signal path 802, the other for adiagnostic beam 1144 connected to a diagnostic circuitry 1140. The ST1122 associated with the diagnostic beam 1144 will continuous switchamong the four beam positions. The diagnostic circuit 1140 will identifythe features of desired signals through power level in a frequencychannels, special codes, waveforms, or other unique features. Once thebeam position for the ground processing is identified based onretro-directive algorithms 1141 and updated new beam positions 1143 whenthe UAV is on station, the beam controller 1142 will dynamically updatethe ST for the main signal path to a new beam position 1143.

The depicted functional block is the 4-element retrodirective antennaarray at Ku/Ka band 1100. The array elements 1132 may featurelow-profile and near conformal designs. Rx multibeam forming processingis through a 2-dimensional Butler Matrix (BM) 1121 followed by a pair ofswitching matrixes (ST) 1122. The first one is for main signal pathwhich is connected to the interface 1102 via a buffer amplifier 1102 a.A first of the two ST 1122 is controlled by a beam controller 1142 whichshall make a decision on which beam positions to switch on to receivethe forward link element signals uploaded by a GBBF facility 412.Similarly in the return link Ku/Ka Tx P/L, the foreground P/L1210 shalldeliver to the interface 1101 a FDM muxed and frequency up-convertedelement signals which are received at a public safety band (e.g. 700 MHzor 4.9 GHz). The FDM muxed signals will go through a ST 1112 and a BM1111. The 4 outputs properly phased by the BM 1111 will then beamplified by power amplifiers 1113 and then radiated by the low profileelement 1132. In the designated beam position at far field the radiatedsignals shall be spatially combined coherently due to cancellation ofincurred phase differentials during the propagations by the pre-phasedindividual element signals by the BM 1111

The current “beam position” decision shall be made based on informationderived by the second of the two ST 1122 which is also controlled by thebeam controller 1142. The second ST will be continuous switched orrotated among all possible beam positions with diagnostic beam outputs.The data collected from the second ST will be used by a on boardprocessor 1140, among other recorded data, to identify a beam positionwhich is currently associated to the strongest signal level of desiredsignals identified via their unique features. The beam controller willthen inform both the Tx ST 1112 and the ST (first of the two Rx ST 112)for the Rx main signals about the current beam positions for theretro-directive antenna.

When the elements are spaced by X the resulting 4 outputs from a BM 1121will be 4 finger beams; each with multiple peaks (or grading lobes).

In Tx, the configuration is identical except the signal flows are inreverse direction. The beam controller will also control the ST 1112 forthe Tx BM 1111.

FIG. 12 1200 is a simplified block diagram for a communications payload(P/L) on a UAV for the communications at regular cell phone frequencybands among the cell phone users in a coverage area. There are fivemajor functional blocks; from top left and clockwise (1) forward linktransmitting (Tx) payload 1220 at L/S band for foregroundcommunications, (2) forward link receiving (Rx) payload 1240 at Ku/Kaband for feeder-link communications, (3) Ground processing facility 410including GBBF processing 412, (4)return link transmitting (Tx) payload1110 at Ku/Ka band for feeder-link communications, and (5) return linkreceiving (Rx) payload 1210 at L/S band for foreground communications.

In the first major functional block on the top right for the forwardlink transmitting (Tx) payload 1220 at L/S band for foregroundcommunications; signals flow from right to left. The up-linked signals1102 received by the on board Ku array 1240 feature “element signals”properly processed by a GBBF designated for the 4 Tx elements 1222 atL/S band. The uplink signals 1102 from the back channels are FDMde-multiplexed 1225 and frequency down converted, filtered and amplified1224 before radiated by the 4 Tx subarrays D1, D2, D3, and D4 1222.There are no on board beam forming processing at L/S band at all.

The second major functional block in the middle top panel is for theforward link receiving (Rx) payload 1240 at Ku band for feeder-linkcommunications. The onboard Ku 4 element array is programed driven topoint its receive beam toward the ground processing center 410. The KuRx beam forming network (BFN) 1241 may be implemented by a 4-to-4 Butlermatrix followed by a 4-to-1 switch or equivalent.

The panel on the right depicts functional flow diagrams in a groundprocessing facility 410 including a ground based beam forming (GBBF)facility 412 and gateways 418 to terrestrial networks. In a forwardlink, in-coming traffic from terrestrial IP network 418 will go throughmany transmitting functions including the modulation for the designatedbeam signals. Modulated beam signals are sent through multibeam Txdigital beam forming (Tx DBF), converting beam signals into elementsignals before frequency up converted and power amplified by Ku Tx frontend 411T, and then radiated by Ku transmitting antennas (not shown)

In a return link, signals captured by Ku transmitting antennas (notshown) are conditioned by low noise amplifier, filtered and thenfrequency down converted by Ku Tx front end 411R, and then sent to amultibeam Rx digital beam forming (Rx DBF), converting beam signals fromelement signals. These recovered beam signals will go through manyreceiving functions including the demodulation for the designated beamsignals which may become outgoing traffic to terrestrial IP networks viadesignated gateways 418

The 4^(th) major functional block in the middle lower panel is for thereturn link Transmitting (Tx) payload 1230 at Ku band for feeder-linkcommunications. The onboard Ku 4 element array is programed driven topoint its transmitting beam toward the ground processing center 410. TheKu beam forming network (BFN) 1231 may be implemented by a 4-to-1followed by a 4-to-4 Butler matrixor equivalent circuits.

The on board feeder-links antennas 1240 and 1230 are conventional“program-driven” and not “retro-directive.”

The 5^(th) functional block is a return links L/S band P/L 1210 forforeground communications. There are four Rx elements D1, D2, D3, and D41212; each of which is connected by a LNA, a BFP, and an up-converter1211 to Ku band. There are no beam-forming processors on board forantennas at cell phone frequencies. The four received signals,up-converted from the 4 Rx subarrays are FDM multiplexed 1215 into asingle stream 1101, which is then power amplified and transmitted to aground facility 4 via a 4-element Ku array 1230. The Ku Tx beam formingnetwork (BFN) 1231 may be implemented by a 1-to-4 switch followed by a4-to-4 Tx Butler Matrix (BM). Each of the 4 outputs of the Tx BM willthen be connected to an active array element.

FIG. 12a is a simplified block diagram for a communications payload(P/L) on a UAV for the communications at 4.9 GHz emergency band amongthe rescue team members. It is almost identical to those in FIG. 12,except:

-   -   1. Operating frequencies of the foreground communications are in        public safety band; such as 700 MHz or 4.9 GHz in US.    -   2. The on-board Ku/Ka feeder-links are via a Retrodirective        antenna array 1100 instead of command driven arrays 1230 and        1240;        -   i. Interfaces are at 1102 for the forward link, and 1101 for            the return link;        -   ii. Details of the retro-directive array are depicted in            FIG. 11.    -   3. Ground processing is identical to that 410 in FIG. 12.

There are three major functional blocks; from top left and clockwise:

-   -   1. forward link transmitting (Tx) payload 1220 at public safety        bands for foreground communications,    -   2. feeder-link payload 1100        -   i. forward link receiving (Rx) payload 1240 at Ku/Ka band            for feeder-link communications and        -   ii. return link transmitting (Tx) payload 1110 at Ku/Ka band            for feeder-link communications, and    -   3. return link receiving (Rx) payload 1210 at L/S band for        foreground communications.

In the first major functional block on the top right for the forwardlink transmitting (Tx) payload 1220 at L/S band for foregroundcommunications; signals flow from right to left. The up-linked signals1102 received by the on board Ku array 1100 feature “element signals”properly processed by a GBBF designated for the 4 Tx elements 1222 atL/S band. The uplink signals 1102 from the back channels are FDMde-multiplexed 1225 and frequency down converted, filtered and amplified1224 before radiated by the 4 Tx subarrays D1, D2, D3, and D4 1222.There are no on board beam forming processing at public safety bands atall.

The second functional block depicted on the right side is the 4-elementRetrodirective antenna array at Ku/Ka band 1100. The array elements 1132may feature low-profile and near conformal designs. Rx multibeam formingprocessing is through a 2-dimensional Butler Matrix (BM) 1121 followedby a pair of switching matrixes (ST) 1122. The first one is for mainsignal path which is connected to the interface 1102 via a bufferamplifier 1102 a. A first of the two ST 1122 is controlled by a beamcontroller 1142 which shall make a decision on which beam positions toswitch on to receive the forward link element signals uploaded by a GBBFfacility 412. Similarly in the return link Ku/Ka Tx P/L, the foregroundP/L1210 shall deliver to the interface 1101 a FDM muxed and frequencyup-converted element signals which are received at a public safety band(e.g. 700 MHz or 4.9 GHz). The FDM muxed signals will go through a ST1112 and a BM 1111. The 4 outputs properly phased by the BM 1111 willthen be amplified by power amplifiers 1113 and then radiated by the lowprofile element 1132. In the designated beam position at far field theradiated signals shall be spatially combined coherently due tocancellation of incurred phase differentials during the propagations bythe pre-phased individual element signals by the BM 1111

The current “beam position” decision shall be made based on informationderived by the second of the two ST 1122 which is also controlled by thebeam controller 1142. The second ST will be continuous switched orrotated among all possible beam positions with diagnostic beam outputs.The data collected from the second STwill be used by a on boardprocessor 1140, among other recorded data, to identify a beam positionwhich is currently associated to the strongest signal level of desiredsignals identified via their unique features. The beam controller willthen inform both the Tx ST 1112 and the ST (first of the two Rx ST 112)for the Rx main signals about the current beam positions for theretro-directive antenna.

The 3^(rd) functional block is a return link P/L 1210 in public safetyband for foreground communications. There are four Rx elements D1, D2,D3, and D4 1212; each of which is connected by a LNA, a BFP, and anup-converter 1211 to Ku band. There are no beam-forming processors onboard for antennas at cell phone frequencies. The four received signals,up-converted from the 4 Rx subarrays are FDM multiplexed 1215 into asingle stream 1101, which is then power amplified and transmitted to aground facility 4 via a 4-element Retrodirective Ku/Ka array 1100.

FIG. 12b is a simplified block diagram for a communications payload(P/L) on a UAV for the communications at 4.9 GHz emergency band amongthe rescue team members. It is for on-board beam forming almostidentical to those in FIG. 12A, except

-   -   1. A on-board multi-beam Tx beam forming network (BFN) 1225B        replacing a FDM demuxer 1225 for the foreground communications        in public safety band    -   2. A on-board multi-beam Rx beam forming network (BFN) 1215B        replacing a FDMmuxer 1215 for the foreground communications in        public safety band

End of Embodiment 4 Embodiment 5

This embodiment presents architectures and methods of implementing UAVbased communications with retrodirective antennas, ground based beamforming (GBBF), and WF muxing demuxing for feederlink equalizations.Equalizations comprise of calibrations and compensation for differentialphases and amplitudes incurred to signals propagating through multiplepaths. Several scenarios are presented as following;

-   -   1. With GBBF and with retro-directive and onboard adaptive        forward link equalization/optimization loop before WF demuxer in        FIG. 13 a;    -   2. Associated ground processing in FIG. 13 b;    -   3. With GBBF and with retro-directive and on-ground adaptive        forward link equalization/optimization loop before WF demuxer in        FIG. 14 a;    -   4. Associated ground processing in FIG. 14 b;    -   5. DBFs in Ground processing facility in FIG. 15.

FIG. 13a is a simplified block diagram for a communications payload(P/L) on a UAV for the communications at 4.9 GHz emergency band amongthe rescue team members. It is for Ground based beam forming (GBBF),same as the functional block diagrams in FIG. 12a , except WFmuxing/demuxing techniques are used for feeder-links calibrations andcompensations.

There are three major functional blocks; from top left and clockwise:

-   -   1. forward link transmitting (Tx) payload 1320 at public safety        bands for foreground communications,    -   2. feeder-link payload 1100        -   i. forward link receiving (Rx) payload at Ku/Ka band for            feeder-link communications and        -   ii. return link transmitting (Tx) payload at Ku/Ka band for            feeder-link communications, and    -   3. return link receiving (Rx) payload 1310 at public safety        bandsfor foreground communications.

In the first major functional block on the top right for the forwardlink transmitting (Tx) payload 1320 at public safety band, as anexample, for foreground communications; signals flow from right to left.The up-linked element signals 1102 received by the on board Ku array1100 feature “element signals” properly processed by a GBBF designatedfor the 4 Tx elements 1222 in a public safety band. The uplink signals1102 have been wavefront-muxed along with diagnostic signals in a GBBNfacility, and are uplinked to a UAV via back channel. The receivedelement signals are FDMde-multiplexed 1225 to recover WF muxed signalswhich are processed by a bank of adaptive equalizers 1324A beforeconnected to a WF demuxer 1324 dx. Many outputs of the WF demuxer 1324dx are then frequency down converted, filtered and amplified 1224 beforeradiated by the 4 Tx subarrays D1, D2, D3, and D4 1222. There are no onboard beam forming processing at public safety bands at all. Some of theoutputs 1326 of the WF demuxer 1324 dx are recovered diagnostic signals1326 which will be processed by a diagnostic processor 1325 to map therecovered diagnostic signals into cost functions which must bepositively defined individually. Total cost as sum of all cost functionsare used by an optimization process 1323 iteratively based on a costminimization algorithm in estimating a set of new weightings for theadaptive equalizers 1324A in each iteration. When fully equalized thetotal cost for the current optimization shall become less than a smallpositive threshold.

The second functional block depicted on the right side is the 4-elementRetro directive antenna array at Ku/Ka band 1100.

The 3^(rd) functional block is a return link P/L 1310 in public safetyband for foreground communications. There are four Rx elements D1, D2,D3, and D4 1212; each of which is connected by a LNA, a BFP, and anup-converter 1211 to Ku band. There are no beam-forming processors onboard for antennas at public safety frequencies. The four receivedelement signals after amplified and frequency up-converted to a commonIF frequency band are connected to many input slices of a WF muxer 1314.A few probing signals 1316 are also connected to many of the remainingslices of the WF muxer 1314 as diagnostic signals. The outputs, or thewavefront component (wfc) ports, are connected to a FDM mux 1215 with anoutput of muxed single stream signals 1101, which is then poweramplified and transmitted via a 4-element Retrodirective Ku/Ka array1100 to a ground facility 1310 shown in FIG. 13B.

The forward link Tx payload and associated return link Rx payload forforeground communications may be in L/S band mobile communications band,2.4 GHz ISM band, or other frequency bands.

FIG. 13b depicts a functional flow diagram for ground processingfacility 1310, which include:

1. receiving processing blocks;

-   -   a. Ku receiving (Rx) frontend 411R,    -   b. WF demuxing 1314 dx and associated adaptive equalizer 1314 a        -   i. an iterative optimization loop with a diagnostic unit            1315 and an optimization processor 1313        -   ii. for equalization of feederlink in return link            directions,    -   c. Rx DBF 781,    -   d. other Rx functions including gateway functions 782        interfacing with terrestrial networks 418 WF,

2. transmit processing blocks;

-   -   a. other transmitting (Tx) functions including gateway functions        752 interfacing with terrestrial networks 418 WF,    -   b. Tx DBF 751    -   c. WF muxing 1324 x, and    -   d. Ku band transmitting (Tx) frontend 411T

FIG. 14a is a simplified block diagram for a communications payload(P/L) on a UAV for the communications at 4.9 GHz emergency band amongthe rescue team members. It is for Ground based beam forming (GBBF),same as the functional block diagrams in FIG. 13A, except the adaptiveequalization for the WF demuxing 1324 dx are used for performed onground as a pre-compensation scheme.

There are three major functional blocks; from top left and clockwise:

-   -   1. forward link transmitting (Tx) payload 1420 at public safety        bands for foreground communications,    -   2. feeder-link payload 1100        -   iii. forward link receiving (Rx) payload at Ku/Ka band for            feeder-link communications and        -   iv. return link transmitting (Tx) payload at Ku/Ka band for            feeder-link communications, and    -   3. return link receiving (Rx) payload 1410 at public safety        bands for foreground communications.

In the first major functional block on the top right for the forwardlink transmitting (Tx) payload 1420 at public safety band, as anexample, for foreground communications; signals flow from right to left.The up-linked element signals 1102 received by the on board Ku array1100 feature “element signals” properly processed by a GBBF designatedfor the 4 Tx elements 1222 in a public safety band. The uplink signals1102 have been wavefront-muxed along with diagnostic signals in a GBBNfacility, and are up-linked to a UAV via back-channels (in feederlink).The received element signals areFDMde-multiplexed 1225 to recover WFmuxed signals which are connected to a WF demuxer 1324 dx. Many outputsof the WF demuxer 1324 dx are then frequency down converted, filteredand amplified 1224 before radiated by the 4 Tx elements (or subarrays)D1, D2, D3, and D4 1222. There are no on board beam forming processingat public safety bands at all.

Some of the outputs 1326 of the WF demuxer 1324 dx are recovereddiagnostic signals 1326 which will be processed by a diagnosticprocessor 1325 to map the recovered diagnostic signals into costfunctions which must be positively defined individually. Processeddiagnostic signals and/or derived cost functions will be relayed back tothe ground processing facility via additional input slices 1316 of a WFmuxer 1314 which is installed for the return link calibrations.

Total cost as sum of all cost functions are used by an optimizationprocess 1323 (in the processing facility) in estimating a set of newweightings for the adaptive equalizers 1324A in each iteration. Theiterative optimization processing is based on a cost minimizationalgorithm. When fully equalized, the total cost for the currentoptimization shall become less than a small positive threshold.

The second functional block depicted on the right side is the 4-elementRetro directive antenna array at Ku/Ka band 1100.

The 3^(rd) functional block is a return link P/L 1410 in public safetyband for foreground communications. There are four Rx elements D1, D2,D3, and D4 1212; each of which is connected by a LNA, a BFP, and anup-converter 1211 to a common IF or Ku band. There are no beam-formingprocessors on board for the antenna elements 1212 at public safetyfrequencies. The four received element signals after amplified andfrequency up-converted to a common IF frequency band are connected tomany input slices of a WF muxer 1314. A few probing signals 1316 arealso connected to many of the remaining slices of the WF muxer 1314 asdiagnostic signals. The outputs, or the wavefront component (wfc) ports,are connected to a FDM mux 1215 with an output of muxed single streamsignals 1101, which is then power amplified and transmitted via a4-element Retrodirective Ku/Ka array 1100 to a ground facility 1310shown in FIG. 14B. The diagnostic signals 1316 will include information(derived data and/or received diagnostic waveforms 1326) on thefeederlink uplink status.

The forward link Tx payload and associated return link Rx payload forforeground communications may be in L/S band mobile communications band,2.4 GHz ISM band, or other frequency bands.

FIG. 14b depicts a functional flow diagram for ground processingfacility 1310, which include:

-   -   1. receiving processing blocks;        -   i. Ku receiving (Rx) frontend 411R,        -   ii. WF demuxing 1314 dx and associated adaptive equalizer            1314 a            -   a. an iterative optimization loop with a diagnostic unit                1315 and an optimization processor 1313            -   b. for equalization of feederlink in return link                directions,        -   iii. Rx DBF 781, and        -   iv. other Rx functions including gateway functions 782            interfacing with terrestrial networks 418; and    -   2. transmit processing blocks;        -   i. other transmitting (Tx) functions including gateway            functions 752 interfacing with terrestrial networks 418,        -   ii. Tx DBF 751        -   iii. WF muxing 1324 x,            -   a. an iterative optimization loop with a remote                diagnostic Tx unit 1325 on UAV, relayed on-board                information via 1315 and an optimization processor 1323            -   b. for adaptive equalizers 1324 a of feederlink in                forward link directions, and        -   iv. Ku band transmitting (Tx) frontend 411T

FIG. 15 depicts an Rx DBF processing 781 and a Tx DBF processing 751 ina GBBF facility 1412. The recovered baseband element signals 78105 by KuRx frontends 411R are converted to digital formats by a bank of A/Ds78101, and replicated into N sets; each for a Rx beam which ischaracterized by a unique beam weight vector (BWV) 78106. Each of theelement signals is weighted in real time through a complex multiplier78102 by a complex component of the BWV 78106. The weighted sum ofreceived element signals by a summer or combiner 78103 becomes one ofthe N beam outputs 78104 of a real time Rx beam specified by a BWV andthe current array Geometry on the UAV. These N beam outputs 78104 arethen sent for further receiving process 782 such as channelization,synchronization and demodulations before delivered to destinationsincluding users connected via public network 418.

For the Tx DBF processing 751, the signals flows are reversed. Signalsfrom different sources are modulated, multiplexed, and grouped intomultiple beam signals 752 designated to various beam positions to bedelivered by the foreground communications Tx array 1222 on a UAV. Eachbeam signal after replicated into M copies or divided by a 1 to Mdivider 75103 is weighted respectively by m components of a BWV 75106.The weightings are carried out by M complex multipliers 75102. For N Txbeams there are N sets of weighted m element signals. The final set ofthe m element signals, as summations of the N sets of the individuallyweighted m element signals, are then converted to analogue formats byD/As 75101 before frequency up-converted and power amplified by Ku Txfront end 411T.

End of Embodiment 5

FIG. 16 features a small deviation for FIG. 1; depicting a scenario ofusing three separated UAVs 120 as three mobile platforms for emergencyand disaster recovery services; UAV M1 for communications among rescueteam members, UAV M2 as emergency replacements of mobile and/or fixedwireless basestations for resident communications via their existingmobile phones and/or personal communications devices using wifi. Thethird UAV platform M4 performs real time imaging and surveillances viapassive RF sensors including bi-static Radars using satellite RFradiations as RF illumination sources.

All three platforms are connected to a ground hub 110 via feeder-linksin Ku and/or Ka band spectrum. The ground hub 110 will serve as gatewaysand have access to terrestrial networks 101. As a result, rescue worksin a coverage area 130 will have access to real time imaging, andcommunications among co-workers and dispatching centers connected by thehub 110. Residents in disaster/emergency recovery areas 130 will also beprovided with ad hoc networks of communications via their own personaldevices to the outside world, to rescue teams, and/or disaster/emergencyrecovery authorities.

The feeder-links of the three platforms M1, M2, and M4 are identical inKu and/or Ka bands. Only the three payloads (P/L) are different; the P/Lon the first UAV M1 enables networks for communications in public safetyspectrum among members of rescue team; the P/L on the second UAV M2 isto restore resident cell phone and/or fixed wireless communications atL/S band, and the P/L on the third UAV M4 is an RF imaging sensor forreal time surveillance.

Three independent technologies are discussed; (1) retro-directive array,(2) ground based beam forming, and (3) wavefront multiplexing anddemultiplexing (WF muxing /demuxing). Retro-directive links forfeeder-links are to make the feeder links payload on UAVs to communicatewith designated ground hubs more effectively, using less power, reachinghubs in further distances, and/or more throughputs.

RF payloads may feature passive sensors such as RF radiometers orbi-static Radar receivers; both of which will feature architectures ofground based beam forming (GBBF), or remote beam forming (RBF), for UAVplatforms 120-M4 supporting and accomplishing designed missions usingP/L with smaller SW&P. Multiple tracking beams from a Radar receivingarray will be formed via a GBBF facility (not shown but similar to theone 412 in FIG. 4) in the mobile hub 110. Dynamic diagnostic beams fromUAV M4 may be used to facilitate the missions.

For the functions of bi-static radar receivers, the UAV M4 shall featurecapabilities of capturing RF radiations from a satellite 140 via adirect path 141 and also those reflected by earth surfaces and objectson or near earth surface via reflective paths 142. Correlations betweenthe radiations from the direct path 141 and those from reflected pathsprovide the discriminant information on the targeted reflective surfacesnear or on the earth surface. Thus the images of the RF reflectedsurfaces are derived.

Many M4 may be deployed concurrently. There are many choices for theselections of RF radiations from illuminating satellites, such as thesatellite 140, for various bi-static Radar applications. RF radiationsat L-band from GNSS satellites at medium earth orbit (MEO) orGeo-synchronous earth orbit (GEO) may be selected by our UAV M4 forglobal coverage. L/S band radiations from Low-Earth Orbit (LEO)communications satellites shall be considered as candidates. Strong Kuband radiations from many direct TV broadcasting satellite radiations orS-band Satellite Digital Audio Radios (SDARS) from satellites in GEO orinclined orbits may be used for land mass or near land mass coverage. Kaband spot beams near equatorial coverage from MEO/GEO satellites, C-bandnear global coverage from GEO satellite, UHF global coverage, and Kuband regional coverage may also be used concurrently for specialmissions using various radiations at multiple spectrums from differentsatellites reflected from same image coverage. These techniques arebased on correlations among signals from two paths; the direct pathsignals as references for “Radar illuminations”, and reflectedradiations as Radar returns from targeted areas or volumes near theearth surfaces.

Multiple received signals from the array elements of the array on theUAV M4 will be sent to the GBBF facility via back channels in a feederlink. Wavefront multiplexing and demuxing techniques will be applied forUAV M4, among many other applications for calibrating back channels infeeder-links, enabling a simple and cost effective GBBF.

GBBF architectures are used for illustrations in here. However, similarRBF architecture shall be developed for the platforms which may bemobile, re-locatable, fixed, and/or combinations of all above to performremote beam forming functions.

The special features for the communications P/L's on UAVs arehighlighted below.

a. Retro-Directivity for Ku Feeder Links

Ku-band arrays are used for UAVs as feeder link antennas to transfer allsignals to and from L/S or C-band elements channels to a gateway where aGBBF processing will perform both Tx and Rx array functions includingbeam forming, beam steering, beam shaping, null steering, and/or nullbroadening for multiple concurrent beams. The Ku band “smart” arrayswill feature retro-directivity via on-board analogue beam formingnetwork (BFN) and beam controller technologies. The 3-dB beam widths areallocated less than 50° for a 2 dimensional 4-element array with elementspacing ˜0.5 wavelengths.

b. Remote beam forming network (RBFN) or ground based beam forming(GBBF).

c. Digital beam forming (DBF) will be implemented remotely using FPGAsand PCs in the GBBF processing located at the gateway facility. Theprocessing will perform far field beam forming for foreground arrays onUAVs. A single gateway will support multiple UAVs; at least one forcommunications network at 4.9 GHz for rescue teams; the other one forcommunity in disaster areas, using existing cell phone bands. The UAVsfor the local community operating at commercial cell-phone bands, and isto replace cell towers which may have been damaged by the disaster.

d. Wavefront multiplexing/demultiplexing (WF Muxing/demuxing). WFmuxing/demuxing transformations feature two unique characteristics; (1)orthogonality among WF vectors, and (2) redundancy and signals security.The first characteristics are utilized for (a) back-channel calibrationson feeder-link transmission for RBFN/GBBF, and (b) coherent powercombining in receivers on signals from different channels on variousUAV. The second characteristics are used for (c) secured transmissionswith redundancies via UAVs.

Furthermore, in most our examples, multiple communication channels infrequency domain as Frequency division multiplexed (FDM) channels and/orsame frequency on various platforms (space division multiplexed)channels have been illustrated. WF muxing/demuxing may be implementedvia concurrent channels in other conventional multiplexed channels suchas TDM, CDM, or combinations of all above.

e. Continuous Calibration Capability in GBBF

Ground processing must have “current knowledge” of the geometry,location, and orientation of the array on board an air platform. Basedon that, a real time continuous calibration capability is designed tocompensate for effects caused by propagation variations, dynamic arraygeometry, unbalanced electronic channels, and/or aging electronics. Thecalibration will include adjustments on time delays, amplitudes andphases among the subarrays through modifications and adjustment on beamweight vectors (BWVs) obtained through real time optimization process.They are highly dependent on the array geometries.

f. Cross-Correlation Techniques

These techniques facilitate the calibration significantly improvingefficiencies on equalizing multiple signal channels for various beampositions. With continuous calibration capability for distributeddynamic arrays, the precision knowledge of slow varying subarraypositions and orientations may be relaxed significantly.

What is claimed is:
 1. A communications system for providing recoverycommunication service to users in a coverage area affected by anemergency disruption of normal communication services, the systemcomprising: a ground hub serving as a gateway to terrestrial networksincluding a dispatch center, the ground hub being configured tocommunicate with at least three mobile airborne platforms roving overthe coverage area via respective feeder-links in a Ku or Ka band; afirst mobile airborne platform of the at least three mobile airborneplatforms, configured to communicate in a first frequency band withemergency workers that are working in the coverage area and associatedwith the dispatch center; a second mobile airborne platform of the atleast three mobile airborne platforms, configured to communicate, inplace of at least one disrupted base station in the coverage area, withuser mobile phones in mobile phone frequency bands or user personaldevices in WiFi bands located in the coverage area; and a third mobileairborne platform of the at least three mobile airborne platforms,configured to generate real-time imaging of surfaces located in thecoverage area.
 2. The communications system of claim 1, wherein theground hub comprises a remote beam forming network to provide remotebeam forming for each of the at least three mobile airborne platforms.3. The communications system of claim 1, wherein each of the at leastthree mobile airborne platforms comprises a retrodirective antennasystem for transmitting and receiving in the Ku or Ka band.
 4. Thecommunications system of claim 1, wherein the ground hub furthercomprises: a remote beam forming network to transform source signalsinto beam signals; a wavefront multiplexer coupled to the remote beamforming network, the wavefront multiplexer performing a wavefrontmultiplexing transformation on input signals that include the beamsignals and known diagnostic signals and generating wavefrontmultiplexed signals; a bank of adaptive filters coupled to the wavefrontmultiplexer to equalize the wavefront multiplexed signals; and anoptimization unit coupled to the bank of adaptive filters to modifyweightings of the adaptive filters based on differences between theknown diagnostic signals and recovered diagnostic signals received fromone of the at least three airborne platforms via a respectivefeeder-link.
 5. The communications system of claim 4, wherein one of theat least three mobile airborne platforms comprises: an antenna system toreceive a signal from the ground hub via a respective feeder-link; areceive frontend system coupled to the antenna system to condition thesignal; a frequency demultiplexing system coupled to the receivefrontend system to frequency down convert and demultiplex theconditioned signal and generate baseband signals; and a wavefrontdemultiplexer coupled to the frequency demultiplexing system to performa wavefront demultiplexing transformation on the baseband signals andgenerate wavefront demultiplexed signals including recovered beamsignals and recovered forward-link diagnostic signals.
 6. Thecommunications system of claim 1, wherein the ground hub furthercomprises: a first antenna system for receiving a signal from one of thefirst and second mobile airborne platforms; a receive frontend systemcoupled to the antenna system to condition the signal; a frequencydemultiplexing system coupled to the receive frontend system tofrequency down convert and demultiplex the conditioned signal andgenerate baseband signals; a bank of adaptive filters coupled to thefrequency demultiplexing system to equalize the baseband signals; awavefront demultiplexer coupled to the bank of adaptive filters toperform a wavefront demultiplexing transformation on the basebandsignals and generate wavefront demultiplexed signals including recoveredelement signals and recovered return-link diagnostic signals; a receivedigital beam forming network coupled to the wavefront demultiplexer toconvert the recovered element signals to beam signals; and a return-linkoptimization unit coupled to the wavefront demultiplexer and the bank ofadaptive filters to modify weightings of the adaptive filters based onat least differences between the recovered diagnostic signals and knowndiagnostic signals.
 7. The communications system of claim 6, whereineach of the first and second mobile airborne platforms comprises: asecond antenna system to capture signals radiated from the coverage areaand generate captured signals; low-noise amplifiers coupled to thesecond antenna system to amplify the captured signals; frequencyconverter units coupled to the low-noise amplifiers to frequency-convertthe amplified captured signals and generate element signals; a wavefrontmultiplexer coupled to the frequency converter units, the wavefrontmultiplexer performing a wavefront multiplexing transformation on inputsignals that include the element signals, the known diagnostic signals,and recovered forward-link diagnostic signals that are previouslyobtained from a forward-link calibration, and generating wavefrontmultiplexed signals; a frequency multiplexing system coupled to thewavefront multiplexer to transform the wavefront multiplexed signalsinto at least one frequency multiplexed signal; a transmit frontendsystem coupled to the frequency multiplexing system to frequencyup-convert and amplify the at least one frequency multiplexed signal andgenerate at least one amplified signal; and a third antenna systemcoupled to the transmit frontend system to receive and radiate the atleast one amplified signal.
 8. The communications system of claim 1,wherein the third mobile airborne platform is configured to perform aradar function.
 9. The communications system of claim 1, wherein the atleast three mobile airborne platforms comprise a group of fourth mobileairborne platforms including the third mobile airborne platform togenerate real-time imaging of the surfaces, the group of fourth mobileairborne platforms is configured to perform multi-static radarfunctions.
 10. The communications system of claim 1, wherein the thirdmobile airborne platform comprises a bi-static radar receiver to captureradio-frequency radiations originated from a satellite via a direct pathand via reflected paths from the surfaces located in the coverage area.11. The communications system of claim 10, wherein the satellite is oneof communications satellites and direct broadcasting satellites.
 12. Thecommunications system of claim 10, wherein the ground hub comprises aremote beam forming network to remotely form beams for the bi-staticradar receiver.
 13. The communications system of claim 1, wherein thethird mobile airborne platform comprises at least one of opticalsensors, infrared sensors, microwave sensors.
 14. A communicationssystem for providing recovery communication service to users in acoverage area affected by an emergency disruption of normalcommunication services, the system comprising: a ground hub serving as agateway to terrestrial networks including a dispatch center, the groundhub being configured to communicate with at least three mobile airborneplatforms roving over the coverage area via respective feeder-links in aKu or Ka band; a first mobile airborne platform of the at least threemobile airborne platforms, configured to communicate in a firstfrequency band with emergency workers that are working in the coveragearea and associated with the dispatch center; a second mobile airborneplatform of the at least three mobile airborne platforms, configured tocommunicate, in place of at least one disrupted base station in thecoverage area, with user mobile phones in mobile phone frequency bandsor user personal devices in WiFi bands located in the coverage area; anda third mobile airborne platform of the at least three mobile airborneplatforms, configured to generate real-time imaging of surfaces locatedin the coverage area, the third mobile airborne platform comprising abi-static radar receiver to capture satellite signals originated from asatellite via a direct path and via reflected paths from the surfaces.15. The communications system of claim 14, wherein the satellite is oneof communications satellites and direct broadcasting satellites.
 16. Thecommunications system of claim 14, wherein the ground hub comprises aremote beam forming network to remotely form beams for the bi-staticradar receiver.
 17. The communications system of claim 14, wherein thethird mobile airborne platform comprises at least one of opticalsensors, infrared sensors, microwave sensors.
 18. A communicationssystem for providing real-time imaging of surfaces located in a coveragearea affected by an emergency disruption of normal communicationservices, the system comprising: a set of mobile airborne platformsroving over the coverage area, each of the mobile airborne platformscomprising a bi-static radar receiver to capture satellite signalsoriginated from a satellite via a direct path and via reflected pathsfrom the surfaces, the satellite being one of communications satellitesand direct broadcasting satellites; and a ground hub configured tocommunicate concurrently and independently with the mobile airborneplatforms via respective feeder-links in a Ku or Ka band.
 19. Thecommunications system of claim 18, wherein the ground hub comprises aremote beam forming network to remotely form beams for each of thebi-static radar receivers.
 20. The communications system of claim 18,wherein each of the mobile airborne platforms comprises at least one ofoptical sensors, infrared sensors, microwave sensors.